If you're in film school, look into internships. If you're not, check your local Craigslist, get in the know with the creative types in your area, and offer to be of service. If you're amicable and trustworthy, people will want to work with you again. And the gigs will get bigger and better each time. A production company is more likely to give a chance to someone with five years of production assistant experience over some kid fresh out of film school. Try to find a production assistant job or another entry level production crew job and do your best.