I had to go visit Rio De Jinero in Brazil for work. It has the higest murder rate, and the highest crime. We did stay out of the bad areas, but in the time I was there, I never saw a single crime. It seemed like any other big city. So, looks don't tell you everything.

Anytime you leave an area unfamiliar to you, you need to treat it as a military operation. Get as much intelligence on the area you are going to including: culture, politics, language, places to see, places to avoid, types of crime, what to eat or drink, and what not to eat or drink.

Always look like you are comfortable where you are at (not scared, or anxious), greet everyone you can with local phrases. Look aware. Keep your head moving, evaluate all targets. Anyone looking at you is probably a problem. Keep an eye on them.

What to do in an emergency? Where are the hospitals? Is it safe to go to the police? Where is the local embassy? Have you registered yourself with the American Embassy (or the embassy of your country). Such registration for Americans allows you access to the worlds largest and most influencial government resources for rescue and evacuation. <img src="/images/graemlins/smile.gif" alt="" />

You probably also want to think about trip insurance, and medical insurance. For around $4 a day, you can get major medical coverage (including medevac to the U.S.), tourist assistance, and even security assistance.

In short, I'm not an expert, and this is all from things I've seen on the web, or told by others. If you are truly concerned, contact a security specialist that is experienced in the area you are travelling.