You need to follow a pull up progression (i.e. start with easier exercises that will lead you gradually to a pull up). Have a look at this one, it's very good:
If you have access to a lat pulldown machine, that's a great way to start. If you don't, get a stool and climb up to the top position of a pullup and lower yourself slowly. Repeat until tired. Do this every other day. You should also do partial pullups, lifting yourself as high as you can and holding in that position for as long as you can. Don't overdo it for the first week or so or you'll be really sore.
Comments
You need to follow a pull up progression (i.e. start with easier exercises that will lead you gradually to a pull up). Have a look at this one, it's very good:
http://www.fitness666.com/2012/06/pull-up-progress...
If you have access to a lat pulldown machine, that's a great way to start. If you don't, get a stool and climb up to the top position of a pullup and lower yourself slowly. Repeat until tired. Do this every other day. You should also do partial pullups, lifting yourself as high as you can and holding in that position for as long as you can. Don't overdo it for the first week or so or you'll be really sore.