1. have something to say
Film festivals aren't a place for mindless entertainment or (for the most part) a showcase of production value. Festivals are looking to include films that make them wonder, question, laugh, cry, or inspire. Find your voice and have something important to say. It doesn’t have to be important to everyone, it just has to be important to you. If you're not evoking some sort of emotional response from the audience, your film probably isn't personal enough. The last thing you want is for your film to be forgettable and lukewarm. If a festival judge HATES your film that's ok because you evoked an emotional response. Sometimes it can be hard to read judges notes like this:
"...the constant repetitive tone of discouragement made it slow and lacking in dramatic development or reversals"
"There are passages that are repetitive and slow with lengthy visual pauses punctuated by a somber music score. Although, painful to watch at times, the sparse dreamlike dynamic somehow works."
No matter how harsh these criticisms might feel, nothing can top the feeling of someone actually connecting with your film on a deeper level and feeling that energy during a screening. Or another filmmaker coming up to you at a festival to tell you how you've moved them, inspired them, and made them reflect on their own life through your film.
Saying something personal with your film puts you in a vulnerable position and open you up to heartache, but comes with greater rewards.