Use since with a specific year or a period in the past > since 2002 / since I was a child
Use for with a number of years > for twenty years
Use ever and yet in questions and negatives > Have you ever / hasn’t been yet
Use already and never, just between have/has and the verb > has already finished / have just been
Use before, since, for, already, many times, so far, yet at the end of a sentence or questions > Have you been there before?