ill say this much.....
the sponsors i have been fortunate enough to attain have been mostly due to:
1) travel as much as you can! either to the bigger events, or even some just around your area. most companies like to get their name out there as much as you can!
2) be nice and approachable... help others, as well as not be afraid to talk to new people. the company reps are actually real people, most are very nice and interaction is good for everyone... and a good attitude is one of the most important things.
3) it is not so much that you win everywhere you go, but be consistent. i dont make the "A" at all the larger events, but most local races i do. and im definitely not the fastest person at my track....
i would also start with some of the smaller, newer companies as they are usually looking for more exposure.
good luck with your quest!