First of all, there is no one specific rule for choosing fundraising ideas for football. Pretty much any fundraiser will work for any organization given the right circumstances. And what are those right circumstances? Basically it all comes down to two things: your sales team (in this case that would usually mean the football players themselves), and the intended customer base. Understanding how these two things work with each other is the key to coming up with fundraising ideas for football that will work well for your team.
A lot depends on the size of your sales team. Is it just going to be the players on their own, or will they have help from the cheerleaders, dance team, or other related groups? If you have a really large group, you could go for a fundraising idea that has higher minimums - for some pre-order fundraisers you can even score free shipping if you meet a certain minimum requirement. Do some quick calculations for each fundraising idea for football you're considering and decide whether it's realistic for you based on how much each individual would have to sell in order to make the minimum order. If you have a smaller group, it might be smarter to go with something like scratch cards, which have a low minimum and can return really high profits.
You also want to bear in mind your customer base when coming up with fundraising ideas for football. If the kids will be selling to their fellow students, a candy bar fundraiser is a sure-fire winner. If the kids will mostly be approaching adults in the community, something like coffee or the green fundraiser my prove more appropriate. Whatever fundraising ideas for football you come up with, as long as you match them to your circumstances you'll be sure to have the greatest success possible.