Related, some inspiration on getting started from the latest edition of Ask a Swole Woman:
So you say you can only manage a few reps, but in fact, a few reps is all you need. The structure of a typical starter strength training program is about three days a week, three movements, three to five sets of about five reps each, and that's it. Then you go home. That's the whole workout.*Buy a terrific, cheap, no installation pull up bar at Amazon.