Any tips on roundabouts? *UK*?

can anyone give me any tips about roundabouts, of course i know that you must give way to those on your right but i'm always a bit wary when approaching and pulling away on roundabouts. also, if someone is on the right lane and you wish to go onto the left, should you wait until they have ped or can you go onto the roundabout as they are not in your destination lane? my driving test is in a few weeks hence all the driving questions!