You just have to learn them carefully and pay proper attention to how they are used. We can only post examples here. But it isn't really going to help. You need to do the work by yourself, I'm afraid.

Look them up in a dictionary.

besides = in addition to "Besides hiking, you can also camp in the park": except = except for = excepting = apart from=with the exception of = but **** all mean "leaving out" of a group of people or things "He visited everybody in his family except for his younger sister." *** "but" has several uses - used as "except" is one of them. It can also be used as a conjunction. You might want to look this up.

You are having problems with the small common words. You should read "keys to words" which you can find at: http://www.bdmadden.com/ The end to your troubles is in the book.