I like this whole idea: getting motivated to start is the hardest part; 1 tends to lead to more once the ball is rolling.

If someone is struggling to do a pull-up, or if someone really wants to "burn out" after their sets: concentrate on the "negative" pull-up.

Jump to the top of the pull-up, then lower yourself as slow as possible, until you just can't do it any more.

you will be surprised how quickly this helps you improve.

Also, if you do over-hand pull-ups with a close grip it will concentrate on your biceps.

Use a door if you need to--cushion your hands by laying a towel over the top.

ps.I generally don't like to "plug" comercial stuff, but I learned those techniques from a book called "You Are Your Own Gym" by Mark Lauren--pretty good stuff for body weight excersises.

pps. I forgot what sub I was seeing this stuff on.