Apparently pull ups and chins ups are different things; I just thought you were pulling yourself up to your chin (I was doing chin ups). A pull up is with palms facing away, chin up palms facing your body; after trying both out, they do feel different and I personally found the chin ups easier. So now my goal is to be able to do one of each.
Many women don`t have the upper body strength to do a pull up/chin up (myself included – so don’t feel bad if you can’t), but with training they can. Another important thing to remember is that the heavier you are, the more weight you’re going to be pulling up (i.e. the harder it will be), the lighter you are the easier it will be.
I have seen some recommendations of training using a cable station or a lat pull down machine, although many others say not to use this to train for a pull/chin up, I do lat pull downs anyway, so I would say do this exercise but it may not help with the pull/chin up.
Basically you just grad a bar and pull yourself up. If you can’t do this, or you can only do a few you can do assisted pull ups until you are stronger. Some gyms have pull up machines (these use a counterweight so that you only pull up part of your body weight), this is what I’m currently using, the plan is to slowly decrease the amount on the counterweight until I can do them on my own. If you are working on these at home or your gym doesn’t have one of these machines, you have a couple of options. You can place a stool under the bar and use only one leg to get yourself up (no leg on the way down though). Another low-tech way to do this would be to place a barbell in squat cage/rack, then push a bench in front of the cage, grab the bar and then place your feet on the bench (butt hanging down off the edge), this way your feet are holding up part of your lower body weight. Finally, you could ask a friend to give you a little boost to get you going.
A couple things to remember: don't swing your body or "kick" yourself up with your hips or legs (this would be cheating), it’s best to use slow, controlled movements. There are many different ways to place your hands, wide apart, close together, palms facing away (pull up), palms facing body (chin up) or if you’re really good you can do a behind the neck. If all of these are too easy for you, you can add weight (via a belt or by holding a dumbbell between your feet).
I am assuming that most people know what a pull/chin up basically looks like, but if not, check it out here: