Decorating with shades of brown and tan is very safe and has a classy look. It is probably easier to decorate with brown tones than with any other colors. If you don't like to take risks with your decorating, brown would be a good color to start with.
Brown is a warm color that makes people feel safe and comfortable. Brown is neutral and won't clash with other colors, which makes is very easy to use. Brown is of course a very natural color, which humans have been surrounded by in nature for ages. Brown is classic and will always look good, no matter what other trends are happening.
If you want to use brown shades, but you want your theme to have a little more interest, make sure you use varying shades of brown to offer contrast. Chocolate brown looks great with light tan for example. Make sure you don't use too much dark brown unless the room you are decorating is well lit. If there is not very good lighting in a room, try painting the walls a light tan, and use dark brown for your accent pieces.
If you want to use brown shades with other colors there are several combinations that look beautiful. Blue looks very nice with brown, it is a very classic color combination that it is hard to go wrong with. Yellow can look very natural and nice with brown. This combination looks very warm and inviting. Red looks great with brown too for a more exciting look.