If there is one thing that should never be overlooked, it is prep for your short or for your feature.
An overlooked thing is filmmakers not doing enough prep!
Here are some pointers and examples of what I mean:
Floorplans
A good floorplan goes a long way. It is an effective communication tool and saves arguments with your Director of Photography ('DOP or 'Cinematographer') on set.
It tells your crew where YOU want to put the camera and can inform on how many setups you actually need. It is an effective tool for blocking, showing exactly where your actor is in relation to the camera and even lights (okay, really your DOP will decide where to place the lights but the camera can be up to the director to decide)!
Here's an example of a very simple floorplan I created in a free version of Celtx (https://www.celtx.com) for a newsreel setup on my previous set.
You can hand draw these or use desktop or smart phone app. I also recommend Shot Designer if you're working off an iPad (https://www.hollywoodcamerawork.com/shot-designer.htm).
Shotlists
Shotlists are a must do for any filmmaker. You'll find them on pretty much every serious shoot more than a storyboard.
I simply create these in word but you can also use Shot Designer for these too.
A shot list will save you so much time on set. I simply go down my shot list while shooting and cross off the coverage I have just shot.
Storyboards
These are effective for visually intense scenes. You don't necessarily need to board your entire film, but they are a great tool and will cement the film in your mind and help you work out your tone.
They will also save you time while working with your Director of Photography and other members of the camera department by visually showing what the shot is.
A fear a lot of aspiring filmmakers have is that their storyboards have to be a beautifully drawn work of art. There is no reason to fear this, a lot of filmmakers simply rely on very simple stick drawings when communicating with their crew. Here's an example of my terrible drawing and handwriting skills.
I hope the above was valuable and helped you with your own creative processes.