1) Wanting to get by someone in a crowded place, "Excuse me, please. I'd like to get by."
2) Interrupting a conversation, "Excuse me for interrupting" or "Sorry for interrupting."
3) Coughing, sneezing (e.g., bodily functions) in public, "Excuse me."
4) When someone says something that (a) you couldn't hear, (b) you didn't understand or (c) you consider rude or offensive, "Exuse me?" or "Sorry?"
5) Stepping on someone's foot, bumping into someone (e.g., an action that causes another pain, grief or discomfort, "Sorry."
Hope those help.