The NHRDA has a contingency program. You sign up at the races, plaster some stickers on your truck, and if you place in the top of your class, you get money!
If you actually OWN some of the products that you have the stickers for, the money is even better!
Example. I just won the ET class at Portland last weekend. If I were running stickers, with no proof of product, I would have taken home around 150 bucks. If I had EVERY product installed, and stickers, I could have taken home 800 bucks!!!!!
I only run one or two of the current contingency products, and I dont run any stickers, so Im not eligible for any money. I just like to race, and I ran the stickers my first year and decided I didnt like THAT many stickers on my truck other than my NWFD stickers.
As for sponsors, its really all about making phone calls. Put together a racing packet, and basically "sell yourself". Why should a business give you money? What does the business expect back from you? Appearances? Name mention? Something more than just a sticker on your truck? Web page placement? Who is watching you race, and why would those watching you be interested in the business your trying to get to sponsor you.
Obviously, approaching the local tree hugger companies about sponsoring a diesel race truck isnt going to help you, so target the businesses that would benefit from a bunch of truck guys watching drag races. Places like a camper/rv sales and service place that wrenches on diesels, or maybe a mom and pop parts store, or 4x4 outfit. The local tire and wheel place?
Also, be realistic about your expectations. Your going to be hard pressed to find someone willing to throw down several thousand in one shot. You might only get a couple hundred bucks. And in this current economy, you may not get any money, but you may get a better discount on parts or service (as in, you still pay for parts, but maybe the "sponsor" eats his own labor costs or lets you use the shop after hours).
Think about it from the business side of things too. What would you say to someone that showed up on your door and asked for money. You'd want to know a lot of details about that person. How long have they been racing, do they look like they are going to continue racing, and not just run with the money. This is where having your "Promotions Packet" ready comes in handy. In it will be pictures of your events, maybe some attendance numbers, how often you place in the upper ranks of your class, the upcoming schedule and when the business owner can expect to see you race. Do you daily drive the vehicle and ppl on the freeway are going to see your logos? How many? Although, if you drive like a jerk on the freeway, maybe having sponsor logos isnt a good idea hahahahaha.