In Britain people normally don't kiss each other when they meet unless they are close friends. In formal situations you only shake hands. When you don't understand you should say sorry or pardon. Don't ever say 'what' - since it isn't polite.
British people are usually very polite and say please and thank you. So make sure you use these words when you ask for something.
At bus stops, in cinemas and in shops the British stand in queues. Don't ever go in front just stand in the queue everyone else.