1.  Use the Jungle Gym off a door or over a pole and train 90 degree assisted chin ups until you can reach 20 reps in a row.

2.  When you can do 20 in a row it is time to move up the challenge to jump negatives. Here you measure the Jungle Gym one hand above your head and pull/jump up until you touch your chest to your hands and then slowly and under control resist down till your arms are straight, then jump/pull back up. When you can do 10 Jump Negatives, then it is time to move up to the next level.

3.  The final level is just doing it, you have passed all the prerequisites, now it is time to start doing chins. Every day do a rep, get used to doing chins. If you are unable to do full chins, do half reps from the top and slowly increase your range until you can do chins from straight arms to touching your chest to the bar or your hands.