Making a short film is quite expensive, they say. However, if you know what to do, you can achieve your goal with very little tools and on a small budget. But let me warn you: it's not a simple task.
You think that buying a camera (even an expensive cinema one) is enough to make a good short film? There are lots of big-budget productions that viewers don't enjoy watching. It's fascinating how it all comes down to the simple paper and pencil work: writing an intriguing story. Just start with "In a world..." and everything else will follow naturally.
A badly shot film can still be saved by a good story, but if you want to take it to another level, get your photography skills sharp. If you are able to photograph beautiful in-camera images with a little or no post-processing, you are probably in good shape for shooting pleasing moving pictures. If you want it to look good, you need a solid knowledge of working with light. If you are used to working with strobes, try to get your hands "dirty" and work with some natural light and modifiers. You better use the free sun instead of an expensive 18K HMI light. No, that's not the price of the light. The price is even higher.
Coming from a photography background and have a good story? You can still make a bad film if your directing confuses the viewers. In film, there's a new dimension: movement of actors and of the camera. If you don't know what to do, try to keep it simple. In order to be good at directing, you have to know the rules and you have to have an experience. Get acquainted with the basics, like the 180-degree rule, where you have an imaginary line in the scene and never cross it. Just tell the story and make sure the viewer will understand it. Don't try to be Spielberg on your first short.
You may write your story on paper towels and shoot your film on your phone with black and white foam core reflectors as light modifiers, but you definitely need good audio. A lavalier microphone is a decent choice, but a shotgun mic and an external recorder is much better. If you are on a very tight budget, write your story without dialogue or rent a microphone and an audio recorder. Do not underestimate the power of audio. To many people, including me, it forms about 60-70 percent of the film impression.
If you study the work of great directors, you may found that there are some of them who mostly like the camera standing on a tripod. If they can make a two-hour feature film on a tripod, you can absolutely make your short in the same manner. If you want to keep the budget low, use a photography tripod, but do not move the camera. It's not meant to be used for smooth movements.
There are lots of great free tools for video editing, especially if you need to cut the film and add some audio and text. Cutting can make or break the film. Again, keep it simple. First make a rough cut and watch it. Take some time away from the film and then come and watch it with fresh eyes. Show it to a few honest (that's very important!) people, and then, refine the cut. I edited my first short film in Photoshop, as it had some limited video functionality.
If you have your paper towel story, your video recording device, and a decent microphone, you can make a great film. Ask friends for help and advice. Video is way more collaborative and expensive than photography, but you can still make a decent film on a budget. Don't get into it with explosions and car chases. Start with a simple message. One of the first films I did a few years ago with a DSLR and a cheap camera stabilization tool that I didn't even use properly can be seen above.