I would also add that YouTube has some great video examples of form for and variations of pull-ups, sit-ups and push-ups! It's amazing what one can do in your own home with only a pull-up bar and some push-up handles. Speed (slow!) and form are much more important than how many you can do, IMNSHO!
I have some plastic ones like these that break down - they are light and I can travel wth them. I think these are important and will spare your wrists from possible strains; they also allow a bit more muscle range.
