Alright, I'll give this question a go. This is all very basic stuff, but I feel I should say it just to show the importance of it.
1. Make a film that's enjoyable for the audience to watch, in this way...
2. Never put something in a film that you think would disturb or repulse an audience. Though still...
3. Make a film that you yourself would like to see.
4. Story, dialog, cinematography and editing-wise, make everything very clear so everyone can understand what's going on.
5. Be creative.
These are just my opinions also, you can do whatever you want in film, but these are just the principles I use most of the time.
That's a very good question though! I look forward to seeing more answers.