From Marrakech take a shared taxi to Imlil, cost 40 MAD per seat. The journey takes 75-90 minutes. The taxis leave from a small market 1km (2 blocks) south of the Bab-er-Rob, bus 35 from the Medina goes there. Taxis can be scarce after about 11:00. There should be no need to change transport at Asni as suggested in some older guide books or websites. If there are not enough people to fill the grand taxi, you can charter it for 300 MAD and avoid the wait.
In Imlil there is a mountain guide agency right next to the car park where the grand taxis are parked. Here a number of people will approach you either proposing the guide you to the refuges or to sell you a map. The maps are not very helpful and are quite expensive! It is perfectly simple to make the walk without a map or guide and to simple ask for directions on the trail if unsure.
Note that recently rules were changed and as of March 2019 a guide is necessary to hike up Toubkal. There are checkpoints along the normal route doing document checks and making sure that a guide is hired. It is not possible to pass without a guide. Although there are different routes going up to the Toubkal base camp (the two refuges), hiker will not be let through unless passed all checkpoints along the normal route. The checkpoints are manned by police or military carrying weapons.
There are currently four checkpoints in place: 1. Aremd 2. Sidi Chamarouch 3. Half way between Sidi Chamharouch and refuge 4. At the refuge itself.
At the first checkpoint there are usually a few locals offering their services as guides. The guides are not free. Minimum price for a guide is 200 Dh (about 20€) per day. Besides the daily rate hiker is also expected to pay for the guide at the refuges for spending nights and for dinners and breakfasts. That means that for the usual two day hike up the mountain a hiker is facing an extra expenses for a guide of 40€ plus accomodation and food at the refuges.
Although a guide is not technically necessary to climb the mountain, at the checkpoins it is explained that there is no way to refuse hiring a guide for hiker's own safety. This doesn't make much sense unless explained that recently there was a criminal accident with two tourists from northern Europe getting killed on the normal Toubkal route.
From Imlil walk to the Toubkal or CAF Refuge, about 4-6 hours, straight up the valley through Aroumd and Sidi Chamharouch. A more interesting route crosses the low pass to the west of Imlil to Azib Tamsoult (keep high and head south once across the pass, 4hrs). Camp or stay overnight at the gite there. Next day continue up the gorge past an awesome waterfall and turn sharp left at a path junction (1.5 hours). Go right at the next path junction about 30 minutes further on. Zigzag up an enormous scree slope to a pass with superb views of Toubkal (3 hrs). Descend easily southeast to the refuges. This is a recently constructed route that isn't shown on many maps.
The ascent is on a good, well-marked path all the way. From the refuges cross the river below a waterfall (difficult after heavy rain). Scramble out of the gorge and follow a good path across a scree slope. Continue across boulders to a stream. Cross the stream and scramble up some rocks (cairned). The path makes a loop to the left, then a steep section threads through some massive rocks. The path continues up the corrie and zigzags up to a col at about 4000 metres. Turn left at the col. You can cut the corner here, but the views are better if you stay close to the ridge. After a couple of false summits you see the true summit with its steel surveyors' tower. Towards the top the ridge itself is difficult, so the path stays on the left (west) flank. Takes about 2.5 hours if you're acclimatized.
There are countless tour companies that can provide you with equipment and guides.
There are two big mountain huts at around 3200m altitude, right next to each other. You can pitch a tent here as well.
Even when only going to the refuges at around 3200m altitude sickness can be an issue. Staying a night or two in Imlil and at the refuges before ascending further can help preventing altitude sickness.