To see the best (and worst) times to visit, please read our reviews of our recommended places to stay
Since the medina is largely car-free, most people walk. If you need help with bags, there are lads with trolleys on hand at key entry points (though most hotels have their own porters for when you arrive/depart).
Outside the city walls, you can take a taxi - this is the best option for going to the Palmeraie. Petits taxis (small cars like the FIat Uno etc) remain within the city limits, while grands taxis are for longer journeys.
Alternatively, caleche rides - canopied horse-drawn carriages - can take up to 4 people on a memorable tour of the city, particularly around the ever-reddening rampart walls at sunset. These can be hired just off Djemaa el Fna. You'll need to bargain hard (don't let them talk you into a long journey like the Palmeraie and back), and the poor treatment of some horses might put you off giving them your custom.