Since I've never really liked the shots of the Enterprise with those spire things sticking out the front of the nacelle caps, naturally these MUST be included. If they're not there, it's not canon and I'll find it difficult to dislike spires that aren't there.
I'll also be offended if the nurse's uniforms have the black collar, since we all know that for some reason, Starfleet nurse uniforms had BLUE collars, unlike even other woman working in science and medicine, and also totally unlike Starfleet doctors' standard uniforms.
Phasers must be gray. Not white, not black. Gray.
Any equipment belts must NOT be light brown, but instead should be black so you can't notice them.
Scotty will NOT have a horrible slicked back hairstyle. If he does, it'll be canon, but totally unacceptable. As with all of the above, I'll refuse to go. Then go anyway. With people who know me.
More than once.
Any scenes depicting tribbles will have to include at least one sitting in the top of a styrofoam coffee cup. If this doesn't happen, it's not canon and I'll drop popcorn on the floor in protest.
One piece at a time...
There are other things too. Let me think...