Lots of practice, as well as observing and sketching your own hands or a wooden artist's model hand from many angles.
A tutorial that contains a bunch of pre-drawn hands that you copy isn't going to help you understand properly how to visualize the shape of the hand in your mind as a 3d object that you can recall and draw at will. The aim of learning to draw hands should be to understand the shape and expression of them in space rather than to copy them or have only a basic recall of what they look like. This only really comes from examining the hand in different attitudes and drawing them from many angles until you understand what they're going to look like from almost any angle.
Art is my job (manga artist and sculptor) and I am still very much learning about hands after many years, so my advice is to start doing this asap. Sooner you start, the sooner you'll be ace at it.
