First, create your proposal.
Write up a three page document, and dress it up with photos and examples of photos you took. Be clear and style it to answer WHY, Who, What, When, and Where. Contact companies in this order; call to get person's NAME who handles these types of requests, speak with that person. If you can't get anyone on the phone; email, but don't be afraid to call to follow up - a no is a no anyway, and a maybe will take your call. You've got nothing to lose.
Second, get organized.
Create an excel sheet with columns titled similar to this: 1. Company, 2. Contact, 3. Contact phone #, 4. Contact Email, 5. Date Contacted and Notes from Call , 6. FOLLOWUP? (yes or blank so it's easy to spot the ones you need to follow up with), then 7 and 8, etc. Repeat columns 5 and 6 every time you follow up.The most important thing is to be genuine and select companies you will be proud to represent. Each proposal should be an honest request to provide value; you have to realize that it's a long term relationship you are entering and it should be a pleasure for you to represent. And remember that to identify these opportunities, it is ultimately a numbers game. Most companies and individuals are intelligent and are using all of their finances in a smart way - so to free them up for your project, it has to be convenient and valuable for you both. It is a privilege to receive support, whether gear or funding, and you should be proud if you get the chance! Get started now and PRACTICE to get better, no one is good at this at first and even I'm still learning. Cheers