Hey Everyone!!

I'm new to the whole travel/frequent flier mile/deals situation. I'm currently in medical school and am hoping to go on a mother/daughter trip to Costa Rica when I graduate (2014). Plus, I'd love to travel just about everywhere after that! I'm pretty frugal and love the idea of flying for cheap/free.

So here's my situation. I've been an AAdvantage member for few years now (with the Citi Mastercard) because AA is the only airline that flies US to Haiti (I've been several times for medical missions!) My current balance is only like 6,000 miles (cashed in on my miles back in November). I'm thinking about setting up accounts with United and Delta as "secondary" miles accounts. Then maybe over (a long) time, those will be lucrative as well.

So what I'm asking is how can I maximize my mile accrual. I don't want to go the credit card route because I've already got student loans out the wazoo and don't want to mess up my credit in the slightest. OTHER THAN credit cards, what are the best deals? I've done some dining/shopping through the AA sites but, again, I'm frugal so my spending is minimal.

Are there any good deals out there? Any advice for a beginner? Where do I look to find new deals?