Approaching Crowd-sourced funding
Before you start any sort of funding campaign, whether it’s Kickstarter, Indiego or word of mouth, you need to have a solid plan in place, but more importantly you need to have your state of mind in the right direction for this, as it is you that is going to be the determining factor on whether you get the support you need for your film - regardless on how many lovely pre-production artwork examples you have with you.
This is probably one of the reasons crowd-source funding platforms such as Kickstarter requires you to create a campaign video with you pitching to the world.
Don't be boastful
Firstly, don’t say things like your film is the best film concept or idea ever conceived, or the most original. Let them be the judge of that; and, secondly, people who are well placed in the industry for a good number of years get tons of scripts and requests everyday.
What you need to think about is how to get them to read your script in the first place, and to do that you need things nailed down before approaching sponsors and contributors
A solid film festival strategy gives people confidence that its worth giving up some time to do work on your project knowing there will be exposure for them, and that the project is not going to just be put on the shelf so that nobody sees it. I have worked on a few projects where everyone on the crew worked their hardest for zero or deferred payment only to never see the film online or screened anywhere due to the film makers not working out the festival and exposure strategy.
Time and budget
Agree up front about what’s required and the time and resource you are asking for the given budget. Stick with that. If you want anything else then its only fair you pay for it or at least come up with a good arrangement rather than play the “you have to commit to it, its your duty etc. card”. Remember they are helping you, and not the other way round.
Always ensure that you register your short film on IMDB and that everyone gets an IMDB credit, as that's always an incentive people starting out in the industry need to get on the career ladder - or anyone, to be honest, who has a serious career in the film industry. If you are submitting your short via withoutabox then you get a free IMDB page for your film anyway.
Whenever you are trying to get people on board and you are pitching to them, don't say "this will be good for your career” or “it will put you on the map". Instead show the support you have gathered already, along with telling them you would love to have their expertise help in making this film a realty by having them join the team. Make sure they are aware that you appreciate their art/craft in what they do and then explain to them the limited budget you have and ask them their advice before asking them to join the project.
The same ethics apply to using Social media (Facebook, forums, twitter etc.) to gather people to support your crowd source campaign.