get better at pull-ups

I have a group of boy scouts who are working on the personal fitness merit badge. They want to know what exercises to do to get better at doing pull ups. Can you all give me some help?

You can place a chair at the bottom of your pull up bar to take some of your body weight off on the way up, and then try to lower yourself nice and slowly. this will help to start to build up your lat's. Barbell rows are also a great way to start strengthening your lat's and chest.

you can also use bands for assisted ones too. also negatives helped me, but i would suggest being careful with that one. i hurt my shoulder & bicep doing them too slowly.