I primarily fly AA, and will be staying at a few Hampton properties in the next few months. I've never had a hotel card before -- is it worth signing up if I don't plan to have many paying hotel stays? I'd be relying on the bonus points mostly. Also, how does it work transferring Hilton points to AA?

With Hilton Brands you can earn both miles and HHonors points. Since you are staying at the hotels, you might as well sign up. Hilton's program lets you choose how you earn:
� HHonors Points and Variable Miles
Earn 10 HHonors Base points + 1 airline mile per eligible U.S. dollar spent*
� HHonors Points and Fixed Miles
Earn 10 HHonors Base points per eligible U.S. dollar spent + 500 miles per stay (100 miles per stay at Hampton Inn, Hampton Inn & Suites, Homewood Suites by Hilton**, and Scandic hotels)
� HHonors Points and HHonors Points
Earn 10 HHonors Base points + 5 bonus points per eligible U.S. dollar spent

You need to figure out how you will spend which option makes the most sense for you. I'm guessing, since you are saying you won't be staying at a lot of hotels, that one of the 1st two options will be best. Go to http://hhonors.hilton.com to find the best way for you to earn.

The conversion rate for HH points to AAdvantage miles is 10,000 points = 1,500 miles. All the details are on Hilton's website

Do you mean you do not belong to any hotel frequent guest program, or that you belong to Hilton HHonors but do not have one of the credit cards that can earn additional points? I might be prove useful to know which rewards credit card(s) you use currently.

I don't currently belong to any frequent guest program. I have several airline mileage cards, but have never been a part of any other rewards program or credit card.

Did you mean to post this in the credit card forum? Seems you would be better off in the HHonors forum. To sort of answer your question, there's no downside to signing up for HHonors, so you might as well do it.