OK
Firstly he has talent but it has a certain naivety that makes me think that he is about 17 years old. He needs to develop a more mature style (I am not talking content here btw just the way he draws)
I would suggest the following:-
Firstly invest in a good quality drawing pad or sketch book and a set of pencils that will give him 6B, 4B, 2B, B and HB. It looks like some of the drawings are on printer paper and one on lined paper out of a notepad. When it comes to drawing its best to get equipped it makes a huge difference to the final outcome,
The picture I like best is the knight. (The 7th picture) That shows more maturity in the style mainly as he has been bolder with his shading. That is lacking in the other drawings. They were obviously done with just a HB pencil. one of the B pencils (6B being the darkest) will allow him to increase the definition between light and dark in the other drawings. (Get bolder...it will make more of an impact!)
The first picture is very flat. This is partly due to the shading but also due to lack of perspective. I would suggest he has a look at some of the online tutorials on perspective to make the drawings feel more natural.
I hope that helps.