Six things that your screenplay should accomplish/do if you want to take it to the highest level. Yeah, no rules, that's not necessarily true there are "non negotiables" that have to be there for an effective visual and dramatic story.  They are:

1. Give Characters at least one strong external goal

2. Place what seems like an overwhelming obstacle in their way that dictates direct conflict

3. Pay attention to character dialogue, if it sounds like dialogue rewrite it

4. Layer subplot with emotional beats that deepen the viewers relationship to the character

5. Start scene in the middle of the action, enter as late as possible and leave early is the saying

6. Use Theme to tie the story together adding that extra emotional connection for the viewer