First, you need a map. Miami's confusing layout makes a detailed map highly advisable. You can buy them at the airport or at any cafe or convenience store. You'll see that most highways run from north to south (Interstate 95 and Florida's Turnpike corridor) and a few west-east (Interstate 75 and U.S. 41 are two of the few routes that approach South Florida from the west). Distances between neighborhoods is immense.

Second and last, you need a car. There is no other sensible option for getting around. The car rules, that is the truth. If you decide to walk, take your precautions because this is not a pedestrian-friendly city. At some places, there are not even sidewalks and the streetlights lack of walking signs.

There are some exceptions: downtown Coral Gables and Coconut Grove. In bohemian Coconut Grove, you can shop until you drop at hip-hop boutiques or designer stores, and have a coffee or a healthy salad at one of the open cafes or hippie style restaurants, and then walk and walk.

Buses are not reliable and you'll spend a lot of time just waiting at a bus stop under the sun. If you like to do touristic stuff, then you can take a Miami hop on hop off bus which takes you around the city and leaves you to the main attractions.