It's best to ask permission if you want to photograph someone, especially if you are working in close. Engage them before you pull out your camera. Learn at least how to say "hello" and "May I make a photograph" in the local language—just showing that you've made a little effort helps. Explain to them what you want to do and what it is about them that made you want to make a picture. If approached in an open and friendly manner, most people will be agreeable—many are flattered that someone has shown an interest in them and what they do. In places where there's a lot of tourism, you may run into people who are tired of being photographed—many tourists are not courteous enough to ask permission, and local people can come to feel abused and exploited. The only way to overcome this is to spend time with the people or to go to parts of the place less frequented by tourists.
Lyn's last tip is to have your own website. "Show off your work on Instagram and Facebook, but do ensure you have a good, easy to use website too. It should have some of your best work (with lots of keywords!), any specialities, and awards/competitions you have won, and your contact details. It's too easy to get carried away, add thousands of images, and forget the basics. Keep it simple."
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.