Exercise at your own risk
Resistance bands are great for all sorts of exercises
Long, looped bands are the best for assisting with chin ups.
Tie the band in a loop onto the bar
Place your knee or foot in the bottom of the loop
If you don’t have a band, and you are training at home, you can place a chair just in front of yourself and place your feet on it – this will take a lot of the resistance and weight from your body/the pull up and make it easier.
How to Tie Resistance Band to a Pull Up Bar
This video shows you exactly how to tie the band on a pull up bar:
Basically – throw it over the bar, and pull one end through the loop:

WOD Nation have a great YouTube channel here
Using a Chair to Perform Pull Ups
I didn’t have a resistance band when I made this video, and couldn’t be bothered finding a chair – so I used a box that I had handy:

When to Do Weighted Pull Ups?
When you can perform 10 pull ups, with good form and technique, then you may want to consider adding weight. The easiest way to add weight is to use a weighted vest, although you can use a belt and attach a dumbbell or weight-plate.
It’s also possible to use an anchor point (a heavy kettlebell or dumbbell should work) and loop a thin/light resistance band around the anchor and your belt. This provide graded resistance which increases as you pull yourself up towards the bar.
Pull Ups with a weight vest:
Do Pull Up Bars Damage Door Frames?
Yes, pull up bars can damage the door frame. My pull up bar that hooks over the doorframe, doesn’t shift or move but still damaged it slightly.