Never forget to plan for everything to go wrong most of the time it will.
Some things are unavoidable and unthinkable but unfortunately they do happen. It's always good to be willing to try and work with people rather than against them.
I think what helps me do well in any department is to have a little confidence in myself and my ability to figure things out, not being afraid to jump right in to something, over planning, giving myself enough time to do something that needs doing, and doing that part of film making as much as you can. I try to volunteer in the things I'm good at first and if someone asks for help on something that I know I have time for and can handle I try really hard to just do it. Helping hands that don't know all the ropes are better than no hands at all. When I was directing I always tried to just get people who are available first. In order to get anyone to do anything for you you have to plan out when you're doing things. Before that even It's a great idea to find locations first. Like an artist you have to think of the background before you can even begin thinking about the foreground. Think about what makes the scene possible first and then think about what makes it pretty. First, get your location and when it will be available and plan your schedule accordingly. Then think about the idea, what do we want the idea to look like shot-for shot. Again you want to over plan for this. Plan out every shot in detail! By the end of this pre-production process keep the ideas in mind but don't marry them. You can then decide what kind of equipment you'll need to make it look like it does in your head. Then you can think about the people available to you that can run all of that equipment, gather them and schedule them promptly. Then schedule back up people for them just in case your first person falls through. Remind those people that they are on-call. Then you should think about the talent. These people at some point will have a level of irreplaceable status. In order to progress and not work backwards you want to stress to these people how valuable they are to this production. Then you can start thinking about the Art-department aspect of it because then your art person(s) will have sizes of the actors to work with. It's ideal to assign a car+assistant/driver to the art department. Think of all the ways you can help them out by donating the clothes, props, make up, and set dressing you can offer to them. Don't be afraid of any stains (unless they're bleach stains) they can all be removed. Then think about all of the luxury items you will want of set; food, coffee, water, snacks, extra scripts, a screw driver, TAPE (ALL THE TAPE), etc.
Then shoot it and expect all of these things to not work out.
Then eventually you can sit down with someone fresh and have them edit all the crazy work you just did. Sometimes it helps to have someone who hasn't so intently worked on this project as much as you have editing the final film. You obviously shouldn't just leave it all up to them, you should watch and compromise and listen to their ideas too. Make some sacrifices your audience will thank you because sometimes as much as you think it's the greatest idea in the world, others might see it differently and that's ok.
Do we have time for this in a matter of 3 weeks. Absolutely not! There are sacrifices you will have to make. I'm not just talking about the pre-production and production stuff that you just planned out for either! Expect to lose money, expect to not eat, expect to have anxiety attacks, expect to have insomnia etc. Personal tolls. But also understand that this is all only temporary. A good film that you can submit to film festivals, that you can show to potential employers and be able to explain how you got to make this film, it makes it all worth the temporary hell you'll have to go through. Your film can last a long long time. Think about the films that literally almost everyone in the world has seen. Those films probably had all of the stress that you have! But they not only made a lot of money off of it, but they got to say hey, I made this and it's really going places! There is a light at the end of the tunnel.
Trust me if you plan like this, and even if everything that you couldn't have even fathomed went wrong, you'll probably most deff. have something worth bragging about. It will make you a better film maker. Your best work will only be your best film because you failed and learned in all the other films before it. Your first film may or may not be your worst. If you put in 100% of your effort, then that is literally all you can do, be proud of that and forgive yourself for being human. Just remember that you can always hug someone when you need to. Unless you're surrounded by cacti. In that case run!
Haven't watched very many films lately, I've watched some documentaries but nothing crazy good.