Shoot great portraits even if you don't speak the language
Asking for permission to shoot a portrait is fairly straightforward even when you don't speak the language of your subject. Smiling and pointing back and forth from your camera to the person is about all it takes. More challenging are cultural differences, overcoming objections and issues of payment.
The issue of payment
There is a range of opinions about whether tourists should pay people to take their pictures. One school of thought is that it simply encourages people to extort ever increasing cash payments from future tourists. Another is that the subjects are providing a service and should be paid accordingly. I see nothing wrong with paying someone for a photo, but only if the person requests payment before you shoot. In some countries or regions I have found that people never ask for money and may even be slightly offended by an offer of cash. In other places, people are quite greedy about the transaction. Generally the more touristy the location the more you can expect to be asked for money. In Cairo, even the local policemen are looking for a handout when you snap a photo. The fact that some ride around on camels and make for great subjects creates an interesting ethical dilemma. And, yes, I did pay the cop in Cairo. In Shanghai, however, I walked the city for hours one Sunday snapping pictures of local residents without being asked for single Yuan.
I often take pictures of street vendors or people engaged in other forms of commerce. In those cases, I make sure to buy some of the vendor's wares, pay with a few extra bills or coins and tell the person to "keep the change." That may not be a great idea when shooting prostitutes or drug dealers, though, so let your moral compass be your guide. Also, I sometimes offer to send prints to my subjects. If you do that, be sure to follow up on your offer. While you can't guarantee that the photos will make it through the mail service, at least send them. You can order very inexpensive 4x6 prints at your local drug store or big box market. For a family with little means to afford the luxury of photography, a few prints of their children can mean a great deal. A photographer who doesn't keep his or her word may make such subjects less willing to pose for other shutterbugs in the future, so if you make a promise, follow through on it.
Getting permission to shoot
Even in places where people are shy with tourists, I've developed some interesting approaches to break the ice. One tactic involves asking permission to take a photo of a person's farm animal or pet. I snap a few shots of the rooster, pig or puppy then show the owner the picture on the back of the camera. That usually warms the person enough for him or her to allow me take a portrait. While showing my subject those pictures, other people usually crowd around to look. I then snap photos of them, too. Using this approach, it's not uncommon for a photo opportunity to evolve in just a few minutes from one of rejection to one where I am stuck taking portraits of person after person for half an hour or more. Of course, I'm always respectful if someone is adamant about not having a picture taken. I can usually tell by the person's facial expression, body language or raised fist. More often than not, though, an initial "no" actually means "I really want you to take my picture, but I'm embarrassed." My collection of people pictures continues to grow, and many of my shots started with a "no." Make sure you understand the cultural norms of the region in which you're shooting. In Muslim countries, for instance, taking a picture of a female without the permission of the father or husband can land you in a world of trouble, just as shooting a picture of a child in the U.S. without a paren'ts permission can unleash a posse of screaming soccer moms.