What is the best and cheapest way to travel across America?

Two of my friends and I, all 18 from England, are planning on taking a gap year and we really really want to travel across America. We were thinking of driving it, but don't really know how to approach it or how much money we would need, and basically how we would secure a cheap car out there. Can anyone help us out? We thought driving would be the funnest way to do it but if anyone can tell us if there is another way we could do it. Thanks!What is the best and cheapest way to travel across America?Best way to see America is buy an AMTRAK North American pass. Good for 90 days and you can stop if you want. Auto rental can get expensive.What is the best and cheapest way to travel across America?hitchhike