1. Have a reason for requesting the photo. Just telling someone they're pretty won't get you far ( especially if you're a mid-age white male...just sayin'.) Find something specific you want to focus on. You can come up with your reason on the fly or even be working on a project ( say, you're really into unique earring photos, or something.) I happened to love this woman's focus on her work. She was making art right there on the spot and her necklaces were awesome so, I told her so...
2. Legitimize yourself. If you're part of a group (like we were) say so. Have cards so people know where they can go to see these photos ( psst, you can see all the group photos here.) Of course, this might not always be practical when traveling, especially when you are barely speaking the same language. Just do your best to give yourself credibility, actually BE credible, and if they aren't down with it, leave them alone. (Chances are, people are more than willing to be your subject.
4. Don't always ask for permission. There's no better way to ruin a great candid shot than telling people you're taking their picture. I know, I know I just gave the no exceptions rule on asking for permission. However, from afar, there is a boundary and you need to be aware of it. Riding that boundary carefully can get you some great opportunities. This is probably how you'll shoot most travel photos of people. Just remember rules 1-3 if you get into their personal space.
5. Don't forget about composition. Once you've scored the subject, don't forget about good composition, non-distracting backgrounds, etc. Sometimes, the shot just won't work. But, othertimes, you have a chance to reposition people, ask them to move into the light, or even move hair out of their face. After getting this guy to move to the side, I tried moving that dread lock over but he liked it there...and that's okay, too!
Marty had a lot of great ideas for composition and themes. He does photo collages and attempts to portray personality without faces. I really like this take and have a couple more tips of my own to add that I found helpful to get the shot...
6. Make your subject comfortable through conversation. You know how you go to the dentist and they start asking you all these questions and you can't really answer because you're jaw is pryed open? Well, same technique but better execution....chat 'em up to make them comfortable! I'm not much for small talk but I found it very helpful to talk while framing up a shot. It really helps eliminate the auto-smile or the blank stare.
Plus, you can focus on whatever you want and they need not know.
7. Appreciate the unexpected. So, you've framed up a great shot of some guy's hair and then his buddy comes and grabs his nipple. Go with it! You can get frustrated or you can capture the experience happening in front of you. (They proceeded to bite each other, too.)