The closest international airport is at Queenstown which services flights from Sydney, Brisbane and Melbourne, plus domestic flights are handled from Auckland and Christchurch. Wanaka Airport is also served by at least two flights most days from Christchurch by Air New Zealand.
Buses from all major cities stop in Wanaka. Timetable . The cheapest option is nakedbus.com  - fares on this service start at $1 if you book early enough. Otherwise try listing a ride on a rideshare site like Wanaka based Cooreea  and travel here with other people.
The town is compact and located on the lakeshore. It is an easy walk to shops and restaurants. A number of operators offer car or mountain bike hire. Also if you're interested in getting around the area, perhaps visit Lake Hawea, there is a new local carpool system that works on a gold coin donation for a ride. For designated stopping/pickup points and more info, check out WanaRide Share 
Wanaka is a mecca for outdoor adventure; trail hikes and day hikes, rock climbing, mountain biking, kayaking, mountaineering, boating on the lake or rivers, horsetrekking, skydiving, scenic flights etc...
Wanaka attracts international tourists year-round.Many are attracted to the region’s huge range of adventure activities, hiking in the rugged and spectacular Mt. Aspiring National Park World Heritage area; or to ski one of Otago's world-renowned skifields - Cardrona, Treble Cone, Coronet Peak and the Remarkables.
You can take scenic flights, go skydiving, paragliding, bungee-jumping, go lake cruising, jet boating or rafting, take a Lord of the Rings tour, go fishing, play golf, climbing, canyoning, kayaking or canoeing, mountain-bike riding or horse riding.
Of just take in its magnificent scenery, explore the stunning Otago Lakes region, go wine-tasting, or exploring historic Arrowtown or Queenstown.
In addition to overnight and multi-day hikes such as Gillespie Pass, French Ridge, Cascade Saddle and etc there are an ever increasing number of enjoyable day walks. Probably the most popular of these and the most satisfying is the Rob Roy glacier hike in Mt Aspiring National Park, closely followed by the circuit Diamond Lake track and the Mt Roy track. New additions include the trail (best mountain biked) out to beautiful Colquhouns beach and on to the Rumbling Burn.
Several operators offer guided cruises out to the islands on Lake Wanaka. Both Mou Waho and Stevenson's island provide wildlife sanctuaries for birds. Mou Waho is a larger island with a small lake which you can walk up to. Lake Wanaka itself is the third largest lake in New Zealand and has a maximum depth of over a 1000ft. There are beaches close by town which offer swimming and sailing or windsurfing, as well as idyllic and virtually deserted beaches 5-10mins drive from the township.
For luxury or more upmarket stays try the following excellent lodges. Riverrun lodge is one such example, alternatively, try Minaret lodge or Lime Tree lodge, both of which are equally exclusive and offer great service. For Lord of the Rings fans, Minaret Lodge offers a themed room, 'Barlimans' as well as LOTR packages.
Maple Lodge on the edge of wanaka has mountain.
Wanaka Resort luxury apartments have balcony views of the Alps. Apartments open onto outdoor living space including pool, jacuzzi, tennis court, gym, barbecue facilities.