This is a WikiTravel travel topic.
Wilderness Backpacking is form of self-reliant travel that affords opportunities to see sights available no other way.
Carrying everything you'll need to survive for several days in the wilderness isn't everyone's idea of a "vacation", but if if you don't mind putting some physical effort into your travel time, it's an ideal way to truly "get away from it all", and hopefully see some spectacular (or even simply pleasant) scenery.
Before taking off on a backpacking trip, assess what kind of territory you'll be traveling through. Distances on a map never look that hard to cover, but once you find yourself staring up at a 400-foot ridge standing between you and tonight's camp, it's a different story. Topographic maps will give you a better idea of what you're getting yourself into, as well as being essential for navigation if you're going off-trail.
Find out what kind of weather you can expect at the time of year you're planning to go. When's the rainy season? What's the temperature range? Keep in mind that going up in altitude is like going up in latitude. Daytime temperatures may be pleasant, but how cold does it get at night?
Check with the local authorities if you'll be using a state/provincial/national park to see what fees there are for use of the park, and for the trails and campsites, if any. In some parts of the world, right to access may give you permission to hike on privately-owned undeveloped land, but elsewhere – especially the highly-territorial United States – be sure to get permission (unless you want to risk prosecution – and maybe even getting shot – for trespassing).
Since "get around" means "walk", footwear is one of the most important aspects of backpacking. Traditional hiking boots could kill a small animal just by being dropped on them (empty) from a few feet up, but modern boots can be much lighter, reducing the drag on every step you take. You don't necessarily need to spend hundreds of dollars on state of the art boots, but odds are your favorite athletic shoes or street shoes will leave you very uncomfortable and hold up just as poorly. But buying a new pair of boots just before your trip is an equally bad idea. Break the boots in, first with short walks, then longer ones.
If the terrain is especially challenging, or if your knees aren't what they used to be, you might benefit from using a hiking stick or a pair of trekking poles (like cross-country ski poles, but without the skis). They aren't just for the feeble; they can improve your balance and increase your pace by adding some power from your arms to your propulsion. A sturdy chest-high branch (not pulled from a standing tree) will do, or you can buy a telescoping staff or set of poles. Some of them can double as a camera monopod, using a mount under the top knob. And while this usage isn't recommended, you'd probably rather face an angry bear with a pole in your hand than without one.
The kind and quantity of clothing to wear depends heavily on the location and season. The key strategy in all but the hottest climates is to layer your clothing. If the temperature is going to vary between night and day (and it probably will), carrying a set of clothing for the warm times and another set for the cool times will take up extra space and add extra weight. Instead bring clothes cool enough for daytime hiking, and bring extra layers to put on over them when it cools off after dark. "Convertible" slacks are handy in warmer weather, allowing you to zip off the legs and turn them into shorts when the day gets warm.
Packing at least one complete change of clothes ensures that if any item you're wearing gets soaked (by rain, a misstep crossing a stream, sweat, whatever) you'll have another to wear instead. This is especially important for socks, which are both the most likely items of clothing to get wet and the most important to keep dry. Spare boots aren't practical, but a pair of cheap flip-flops will give your feet a chance to breathe when you're not on the trail, and give you something to wear after you accidentally dunk your foot in a pond while collecting water.
Although cotton is comfy and breathes nicely, it doesn't dry easily, making it a less-than-ideal choice for items you'll be wearing next to your sweaty skin; synthetic fabrics can better keep you both cool and dry. Cotton also doesn't keep you warm when it gets wet; wool is a better material for your socks and outerwear.
Do with this information what you wish: Humans in many cultures across countless centuries have lived without freshly laundered underwear every morning.
There are two basic kinds of backpacks used in wilderness travel: internal frame and external frame.
The external frame is the more traditional variety, consisting of a metal frame that's strapped to your hips and shoulders, and which your sleeping bag, tent, and the fabric pack itself are strapped to. They're better for keeping your gear organized and accessible, and a bit cooler to wear, because they leave small gaps for air to move between you and the pack. They're the best option for the heaviest loads.
Internal frame packs have become very popular in the last couple decades. They use a flexible plastic frame built into the fabric of the pack itself, which allows you to carry more of the weight closer to your body, improving your balance. One trade-off is the lack of back ventilation. They also tend to have fewer internal compartments, with everything stuffed together inside, making it harder to get at things on the trail.
With either kind of pack, be sure to adjust the straps to put as much weight as possible on your hips, rather than your shoulders. The shoulder straps should mostly be keeping the pack from falling backward, not actually supporting its weight. This will save lots of wear and tear on your back and shoulders, making for a much less painful trip.
Some people prefer to bring along at least one of anything they might need, and others opt to travel more lightly, giving up inconvenience and comfort for mobility. But if your pack weighs more than a quarter of your body weight, it's too heavy.
You'll want "light" meals, not in the sense of fat or calorie content, but in terms of how much the food weighs in your pack. In fact, you may want to lay off a lot of your "healthy diet" habits for the duration of your trip, because you'll want those extra calories, and fats are a good compact source of all-day energy. Backpacking is the very kind of lifestyle that led homo sapiens to develop a fondness for that kind of food. Depending on the length of your trip, food could make up a substantial fraction of your pack weight. Since water makes up a large percentage of the weight of most foods we eat, and can be found along the way, the obvious solution is to pack foods you can "just add water" to.
Some campsites have fire pits or grills available for cooking. If you use these, limit the wood you gather to small branches taken from the ground, not anything broken from trees (living or dead). It's not as folksy, but it's more considerate of the environment to bring a small gas-powered camp stove with you: they're safer, more efficient, and don't require scavenging firewood from the wilderness you're there to admire.
Keep pots and pans to a minimum, both for weight and clean-up reasons. If camping with someone you're in the habit of kissing, sharing a pot of food instead of dishing it out onto plates isn't exactly a hygiene issue. In fact, if you mix and eat your freeze-dried meals in the packages they came in, and your oatmeal in the baggies you packed it in, you can get away with just a single pan for heating water, which won't even have to be washed. Stick to stewy and spoon-able entrés, and you may not even need to bring a fork or dinner knife.
Be prepared to drink more fluids than you're used to. The reason overweight people sweat more than thinner people isn't just because they're well-insulated; it's because they're carrying around extra weight... just like a backpacker. If you're at your ideal body weight but carrying a 40-pound pack, expect to sweat like someone 40 pounds overweight.
You might be able to pack all the water you'll need for short trips of a couple days, but not for anything longer. Some areas will have wells that you can pump to refill your water supply. In more remote areas, you'll have to collect water from lakes and streams. Check with the local authorities to find out what precautions they recommend for these water supplies. Depending on what micro-organisms are common in the area's water, they may recommend using water purification tablets (a dose of poison strong enough to kill many bugs, but not affect humans), micropore water filters (usually pumped by hand), or boiling the water for several minutes. Boiling isn't usually a problem for cooking water, but filtration or chemical treatment are less hassle for water you'll want cool enough for refreshing drinks as you hike.
Lightweight synthetic insulating materials have been developed for sleeping bags in the last few decades, but ye olde down remains a good option. Down still offers the most warmth for the least weight and it packs up more tightly than synthetic fill, but it loses its warmth-keeping ability when it gets wet and takes longer to dry. Down-filled bags last longer but are also more expensive. Mummy-style bags will keep you warmer than rectangular ones (less space for your body to heat up) and take up less room in a tent, but don't plan an moving around much in your sleep in one.
The fluff in a sleeping bag is only to keep the air inside warm, not for softness. Cold ground can suck the heat out through the flattened underside of a bag as well. For these reasons, a thin foam pad will make your nights far more comfortable. Instead of a pillow, try wrapping the clothes you aren't wearing in your towel and rest your head on that.
Some backpacking areas have shelters along the trails, spaced at intervals a typical hiker can cover in a day. If these are available, and the park authority lets you reserve them, you may be able to dispense with carrying a tent. This doesn't mean you can use a lightweight indoor "slumber party" sleeping bag, though; even if these shelters are fully enclosed, they probably won't offer much protection from cooler night-time temperatures.
Tents are available in many shapes, sizes, and levels of protection. Some models (especially domes) can be free-standing, requiring no stakes to hold them in shape. They tend to be heavier and trickier to set up, though. Unless you're sure you're never going to get rained on, a tent with a "rain fly" – a water resistant tent for your tent – is essential.
At the low-capacity end is the "bivy sack", which is little more than a raincoat for your sleeping bag. A typical 1-person tent will give you enough room inside to actually hunch over and maybe even turn around. A 2-person tent is going to be big enough for just that: two people. Depending on just how close you and your camping partner want to be, you might prefer a 2-to-3-person tent (usually big enough for two adults and a child). If it's just that you want to keep your gear close by (whether for access or to keep it out of the weather), a tent with a vestibule or an extended rain fly might do the trick. Either take turns carrying the tent, split its components up between you, or have one person take the tent and the other the cooking gear. By the time you get to a 4-person tent, you're talking about something heavy enough that distributing the components among the people in your hiking party is pretty much essential. The good news is that these are generally spacious enough that one or two people can sit upright in them.
Although tents will keep the wind out and usually trap air well enough to keep it warmer than outside, don't count on them to keep you warm; that's your sleeping bag's job. The difference between a 3-season tent and a 4-season tent isn't their warmth, but the latter's ability to stand up to stronger winds and snow.
If you're traveling in an area without established campsites, you should always follow leave-no-trace camping principles for making and breaking camp, as well as your other activities in the wilderness.
Stay safe and healthy
Take care of your feet: they're what's getting you home. If you start feeling "hot spots" on them, take care of them quickly before they develop into blisters. Moleskin offers the best protection, but if you don't have that, adhesive bandages or even tape will help protect these spots from friction.
If there's cell-phone service in the area you're hiking (and don't assume there will be), bringing the phone along (turned off, to preserve both the battery and the atmosphere) is a reasonable precaution in case of emergency.
Even if there are maintained outhouses along the trail (again: don't assume there will be), you shouldn't count on them having toilet paper; bring a partial roll from home. If you're unsure about the availability of facilities, bring a garden trowel so you can dig and then cover your own single-dump latrine (well off the trail and far away from any water supplies).
See also altitude sickness.