Avoid characters that are related somehow to an established on-screen/treklit character unless we've already heard of them.
Don't have the characters quoting themselves from episodes and movies.
Avoid matching up a character's ethnicity to the name of the ship he/she commands (i.e. having Chekov command USS Potemkin just because it has a russian name).
Keep hybrid characters to a minimum. Vulcan/humans, bajoran/cardassians, Borg/Magnavox, whatever. These types of folk should be rare.