Speaking strictly as a viewer and not as a maker of fan films, one suggestion I'd have is to avoid making your film or series an example of what I've dubbed "YASYAC" -- Yet Another Ship, Yet Another Crew.
So your show or series is about the Whatchamacallit-class USS Thingamajig, launched on stardate xxxxx.x. The captain is a 47-year-old, androgynous, one-third human, one-third Ferengi, one-third water buffalo, your first officer is a Betazoid-Andorian-Caitian-Excalbian-Talosian-Sheliak hybrid, and the deputy chief engineer's name is Hank.
Why should I care about your ship and your crew? What's the compelling reason to watch? What is it that distinguishes the USS Thingamajig from the USS Yadayadayada?
I would encourage fan filmmakers to put a unique twist on their projects -- something to make their works stand out in some way.