I hope this is the appropriate board for this.
When I go to read a fan fiction, I am expecting a few things.
1. An actual plot, not just endless graphic sex between the author and their favorite Beatle. or worse, slash fiction. Don't even get me started on how wrong that is.
2. Humourous parts. Even if you have a serious story, you should add some funny parts to keep your reader's interests. No one wants to read 50 chapters of tearful dialouge or inspirational speeches.
3. Secondary characters! It doesn't work unless you have some characters who are fictional or at least not a Beatle.
4. No unnecessary singing. Have you ever read a fan fiction where the whole thing was set to crappy music, like "Hopelessly Devoted To You"? Granted, Beatles music is not crappy at all, but I'm not looking for songs here, I'm looking for stories about the Beatles.
5. No references to modern day. If you're going to set your fan fiction back in the 60s, mentioning the things of today is a big no-no. The only exception to this rule is if you are time travelling in the story.