The following was taken from a thread way back in 2004 called "ZEB On Chin-Ups". Following this program I vastly increased my Chin-up numbers. This is only part of the complete post as it is rather lengthy.
Here you go:
When you are trying to add reps to the total you want to make sure that you are training Chins three times per week! I agree with Pavel who stated that greater "synaptic facilitation" (greasing the groove)occurs when you are doing them more frequently. I do not agree that you should train them everyday, as Pavel suggests. I think this leads to burnout, and I have been there as well.
I begin what I call "intensive training" about four weeks away from a Chin contest. This means that I cut back on most of my other exercises and focus primarily on Chins and Pulls. Keep in mind that I always add 3 or 4 sets of overhead presses as I feel that you need to balance a "verticle pull" with a "verticle Push." Most of the other exercises that I normally do such as squats, deads etc are dropped from my schedule four weeks out.
This also has a strange effect on the body. Since your body wants to stay at a certain weight it tends to sort of shift the weight from say your legs to your lats and biceps. This does not occur to a large extent, but it does happen and it helps a great deal.
We are doing 12 training sessions. That is 3 workouts per week for four weeks. We are really going to go for the reps now!
I am going to perform 5 sets. 3 sets of Pull-ups and 2 sets of Chin-ups. All reps should be performed in perfect form, with maximum speed! You may wonder why I am recommending Pull-ups, since it is easier to perform more reps with Chin-ups. I do this for two reasons: First, The Lat muscle is worked harder with a Pull-up than a Chin-up. When we turn the hand around (palms facing you) you are doing a Chin-up and you are also allowing the bicep muscle to do more work. This is great, you want strong biceps, but the lions share of the work needs to be done by the Lats!
The Lats are a larger muscle and therefore need to be trained to do more of the work. The lats will get more work with Pull-ups (palms facing away from you) than with Chin-ups. So, I like to train mostly with Pull-ups in order to get more Chin-ups in the contest.
The second reason that I train more Pull-ups than Chin-ups is that I have noticed through the years that people tend to injure their forearm tendon doing to many Chin-ups. You may have experienced this. It can become so sore that you can't even make a closed fist. When performing a Pull-up this does not occur.
I begin workout one by doing reps in the 33% range of what I want my one set total to be in the contest. For example, last summer I was shooting for 30 reps (I got 31). So, I trained with 10 reps in that first workout (four weeks away). I did 3 sets of 10 Pull-ups with a 2:00 rest in between each set. I then waited 3:00 and did an additional two sets of 10 in Chin-up style. Rest periods can climb as the reps do. I like to add about :10 to :30 of rest each week (starting with a base of 2:00) between each set. If you are unable to get your required reps don't force it out. Drop from the bar count to :10 (or more if need be) grab the bar and complete the set.
When training for reps forget about short rest periods between big sets. You need to rest and recoup in order to put up the big numbers. sort of like how a power lifter trains. You do not see a power lifter resting two or three minutes between sets. They rest a long enough to recoup. We won't rest as long as a typical power lifter, but we will rest longer as the reps go up.
I then gradually take the numbers up. the 2nd and 3rd workouts, of the first week, I do 40% and 43% of the one set goal! Again three sets of Pull-ups and two sets of Chin-ups.
The second week I am doing 50%-53% and 60%. Third week:60%-63%-67%. On the fourth and final week I switch to all Chin-ups in order to nail that specific groove. I also lower the sets and try to raise the number of reps. When I do this I also raise the amount of rest time between each set from 2:00-3:00 to 4:00 to 5:00 and sometimes a bit longer.
For the final week I am at 75%-80% and 85%. I am now only doing no more than three total sets each workout. On the final two weeks I also do two sets of negatives, no more than 10 reps per set, with a 10lb wt. belt on. I perform negatives in the top half position as this is my weakest point. If you have a hard time getting out of the hole then do negatives in the bottom half only.
Good Luck My Friend!