You are a high priority target for robbery, kidnapping, extortion, scamming, murder, and a host of other things from the lovely locals you're mingling amongst. Stay to well lit areas, don't stay out late, don't follow anyone around, dress in a way that does not draw attention to yourself (better if you can get into local garb), and assume every single person is there to kill you. Limit your drinking, and if you do drink do so amongst expatriates and travel friends, and guard your drink at all times.
People do not like Americans. Many times their ill will has at least a logical foundation. While I certainly appreciate the state department attempting to manage image this isn't enough. Americans must be on the defense at all times. You must especially be defensive in non-western countries (where you are probably better off simply not going). While many people are easy going the mixture of zealous propaganda about Americans, and America's own negative image, will have you perceived as a target more often than a friend.