just passed my 6 week mark, headed back to the gym finally!!

I was told to wait 6 weeks to start working out besides walking.  Well I'm there now and a couple years ago I took spinning classes 3 times a week and LOVED spinning.  I don't know that I should jump back into that right away.  What are things you started doing to build your body up to handle more vigorous exercise?  What are your favorite things to do working out??  I'm so happy I'm going back.  I truly enjoy working out.