I have had two sponsors
my first I sort out and sent in a letter stating what I could offer them with photos etc.
this was after winning a few local shows.
after starting to win overalls and being mentioned as a possible national class winner my current sponsors approached me - it helps if you bring something to the table, I am active on alot of non sponsored forums (unlike this one)and write for magazines etc so not only do a publicise the sponsorinjg company at shows but do it on a regular basis in a wide variety of places.
think of it this way - if you had a company what would make you offer money from your own pocket to others in return for?