Tips for writing better fan fiction:
1. Angst does not always equal good drama.13.
2. Relative length is in no way proportional to quality.
3. Show, don't tell.
4. If a character has never referred to another character by a pet name, then it is not always very likely that they would start now, even if they have entered into a romantic relationship. Keep your character's traits in mind when you decide to write this into a story--it can be a bit of a stretch for your reader, otherwise, and undermine the integrity of the story you are trying to tell.
5. Don't set out to write a series. And don't advertise segments of a series if they have not yet been written. It's pretentious and often very, very annoying. Even if you're Robert Jordan.
6. Don't base stories off of popular songs or films. Likewise, don't name stories after popular songs or films unless it's extremely clever and original. 99 times out of 100, it just looks silly.
7. Stories should have a plot. That plot should having rising action, a climax, and then falling action. Even if you are writing a character-driven vignette, you still need this structure.
8. Spelling counts.
9. Grammar counts even more.
10. If you research your topic (be it researching the Trek universe socio-political climates during a specific period of UPF history, or Iowa in the 1950s) your story will be the better for it. Treat SF like a period piece--same as any historical fiction. Whether it's a western, or a Trek story, you are still creating a solid landscape for your reader.
11. Once you set up your universe's rules, stick to them.
12. If you're going to write time travel, make sure you understand time travel. Or else, your readers will never understand time travel.