http://marrakech.airport-authority.com/ is the updated webpage address (2011).

When you are arriving into Marrakech you will need to complete an embarkation card before arriving at the front of the queue for passport control.  Embarkation cards are found near to the entrance door or may be passed out on your flight. Once you have collected your luggage, you will come through the doors into the main hall area. Marrakech airport can be very busy so expect up to an hour after landing to have passed before you finally emerge into the arrivals hall.

Immediately outside the airport you will find both petit and grand taxis.  There is a board detailing the prices to the various parts of Marrakech, however the drivers do not usually follow this guide!  For Gueliz/Hivernage/Jemaa El Fna try not to pay more than 100Dhs.  For riads in the medina expect to pay 100-200Dhs.  For the Palmeraie expect to pay 150-200Dhs. For new hotels (2011) along the Route d'Ourika it could be up to 300 DHs. Many hotels offer airport transfers and this could be a sensible option depending on price.  Prices are for the whole taxi, not per person, and include your luggage.  There is also a bus (number 19) which arrives at the airport approx. every 30minutes and drops off at various locations around the city. You pay the driver directly. 

If you are on a very tight budget, you can get local bus #11 from the main road (turn left when you have crossed the airport parking lot - good luck dodging the taxi drivers) for about 4 dirhams.

Marrakech airport is very close to the city; 15 to 20 minutes drive from the main square, Jemaa el Fna.

When departing the country, DON'T forget to go to a bank in the terminal BEFORE going through customs/security - as after you have passed this area you will be unable to exchange your dirhams! There are some outlets which take dirhams but the duty free shop will not.  You can keep up to 1,000 Dirhams however you can only exchange it outside of Morocco at a few airports and get a very poor exchange rate. There are charity collection boxes for small notes and coins. The duty free shops are all priced in Euros and will take credit cards.

Before you go through to the passport control you need to have completed a debarkation card (exactly the same card that you completed when you arrived).  You will find the cards in the check-in area and near to the door for the passport control and the departure lounge.
Most people recommend you arrive at the airport 2 hours before your departure time as it can take a long time to get through depending on the number of flights leaving.

In the departure lounge you will find cafes, duty free and other shops and a smoking area in the far left corner. There is ample seating in front of the departure gates and all departure gates are visible - very straight-forward.

An alternative to flying is the train from Tangier --the Marrakech Express -- 21:30 every night from Tangier arrives 08:45 next morning. Return from Marrakech is at 21:00 each night 07:30 Tangiers next morning. price incl. couchette is 285 dhm one way. price of small taxi from the staion to the sqaure should be 20 Dhms.