There's definitely not an easy answer to this question. I'd highly recommend reading any documents that other successful teams have on the topic for pointers and ideas.
I do have one small piece of advice though. You should plan lots of smaller fundraisers, i.e. <$1000, instead of going exclusively for the big money. I can almost guarantee you'll be more successful if you take that route.
In today's uncertain economic times, having a diverse sponsorship base of smaller donors can potentially be more sustainable than one or two major sponsors.
Good luck raising that money!
