The Middle Pause Pull Ups are a great Calisthenics exercise that helps in breaking the stick point and improving the last part of the pull up. This exercise can be very good for all levels, as its intensity can be easily modified. The easiest way to do it would be to add an elastic band and the hardest to add as much weight as you can.
In this specific variation the pause of the Pull Up should be done where you have your stick point. This will force you to accelerate again from your sticking point in order to overcome the bar.
1- To start you need to do like a regular pull up until you reach your stick point.
2- When reached the stick point you need to pause the vertical movement of the pull up. This means you need to fully stop the ascent. The pause needn't be too long, once you are paused, you can keep pulling.
3- The top part should be the hard one for this exercise. Make sure you finish the pull up as hard as you can. Try not to lose the scapula position (retraction and depression) in the final part.
For further Pull Up Specifications, see our post about 10 Tips To Improve your Pull Up.