My husband and I married in college, and one thing we wish we'd done sooner is to plan ahead for those occasional and unexpected large expenses like medical bills and car repairs. We kept close records of how much we typically spent on these expenses in a given year, divided by 12, and then set aside that amount each month so that we could avoid using credit cards to cover the costs. It was hard to do because we had to cut back substantially in other areas, but it was worth it for the peace of mind. When money is really tight it's easy to use large car repairs/maintenance as an excuse for going into debt. For more info, I recommend the chapter on "Freedom Accounts" in "The Complete Cheapskate" by Mary Hunt.

Have an idea of where you want to be after college and start saving while still in school... then you can avoid that after graduation let down and get going while still bright eyed and filled with post-grad excitement!

Do all that you can to live a solid lifestyle starting in college. Research the free or reduced cost activities around campus. Make youself eat in the cafeteria instead of going out. Get a simple phone, instead of a cell with all the bells and whistles. Learning to live like that will help when you graduate.