Always have your camera with you and always keep your eyes open. Serendipity plays an enormously important role in travel photography. You never know what you are going to run into, and you have to be ready. Many times you will see what could be a good photograph but decide that the light is not right, or there are no people around, or too many—something that means you will have to come back later. But sometimes you get lucky. You happen to stumble upon a scene at just the right moment. If you forgot your camera, are out of film, or your digital card is full, if you have to fumble around getting the right lens on, the moment may be gone before you can recover. This is true whether you are doing street photography or visiting a natural or man-made site. Mountains, trees, monuments, and other static subjects are, of course, not going to go anywhere, but the ray of sunshine, the soaring eagle, or the embracing couple that add the needed element to your photograph are unlikely to hang around. Think of it as hunting—whenever you leave the confines of your camp, you should be ready and able to capture whatever pops up.
Make use of people to give your images life and scale. If the facade of a particular building appeals to you, the picture may be that much better if you show people walking in front of it. They will give it scale and also let viewers know what sorts of people live there, how they dress, and the like. An outdoor café may be more interesting crowded with people than empty.