I try and follow a rotation where I do cardio either 30 or 60 minutes a day. 30 if I add weight training which I usually do 2 or 3 times a week for 30 minutes. To learn how to use free weight correctly you could join a body pump class if they offer it or check out a magazine like "Women's Health" the book "Body for life" or this website
http://www.stumptuous.com/cms/displayarticle.php?aid=41 has a lot of great info. Also, try and add an active rest day in the mix. This is a day where you only do light cardio (walking the dog) and stretching.
Good luck, remember to much can lead to burnout or boredom so make sure you aren't stressing your body.