Don't accept any offers from anyone here, I know it's harsh, but this village is hustler central.
Currently duplicated in Imlil
It takes about 2 hours to get from Marrakech to Asni. There are buses from the central bus station which ostensibly leave every 30 minutes (although this is not what we found). We found a quicker way was to take a petit taxi to the out-of-town grand taxi 'park' (cost 15dh. If you're better at haggling you can get this lower, if you care about a few pence). From there, a grand taxi will take you to Asni (cost 90dh split between 6 of us[Grand taxis are maybe not the way, if you don't like sharing very confined spaces with strangers. However, we got on well, swapped food and drink, etc]).
Alternatively, if you are staying at Kasbah Tamadot, private transfers are available from the Marrakech airport to the resort.
Asni describes both the small village where the grande taxis drop you and the wider valley, however if we just consider the village: It is split into two parts. The 'commercial' area, down by the main road. Here there are shops lined up on either side of the road. Behind the shops up a slope to the South(?) a short distance is the 'residential' part of the village, consisting of 50 or so houses.
Obviously walking on foot is the way to get around (as the village is only a few hundred metres wide).
This village has little to see. We were taken to the smaller residential part while waiting for a van to take us to Imlil. These small old mud-brick houses seem amazing the first time you seem them, but you'll see more, higher up in the mountains, without all the touts and conmen.
For many people there's little to do here beyond buying food and water, and leaving. Okay, that's a bit harsh. Asni has many hammam (bath houses), which would have been nice after long walks in the day. It has a weekly market too, selling meats, haircuts, metal work, etc...(unconfirmed!)
Food, Water(probably a really good idea if you're planning to head further into the mountains. Bottled water gets more expensive the further you get from Marrakech? And if you feel like being conned, there are Loads of really naff trinkets being sold by hustlers.
The weekly market might be worth a look too. However, remember Marrakech probably has everything you can buy here, at half the price.
There are a couple of cafes on the main street, but we didn't try them.
Others report some have very good food.
This is rural Morocco...Alcohol is illegal
There is one hostel and one hotel (apparently, would like this confirmed).
Additionally, Sir Richard Branson's new luxury Moroccan retreat is in Asni. It features a total of 19 rooms and suites.
To get back to Marrakech a grande taxi back is the best way. Warning: Taxis back to Marrakech are in general more expensive than coming here. The is because people often travel through the mountains, so theres less people coming back to Marrakech (apparently...)
To go on up into the mountains, please read the Imlil page.