Its about personal relationships as well. If you actually have a relationship with a potential sponsor, that will go a really long way. Recommend that you make a list of all sorts of people you know and approach them for support. I had all my accomodation, transport, meals and fees paid once by a sponsor just cause I asked and everyone was too scared to approach him for fear of being declined! So being bold and upfront can also pay dividends.

But be realisitic as well, racing does require you to put a lot of your own time and money in, if you can convince others to pay for your playtime all the better!