Direction

The study table should face east or north direction. North is also acceptable to certain extent. West and south directions should be avoided.
Position
Yes, it is advised not to position the table against the wall. It should be 3-4 inches away from the wall to allow easy flow of air, light and positive energy. Facing blank wall should be avoided, since it curbs free thoughts and creativity. Instead hang a poster of an inspirational quote or message, which will keep the child focussed on the ultimate goal. A poster of greenery could also be hung, since looking at something green every 20 minutes refreshes the eyes. It is advisable to choose something subtle and not something gory and gaudy, which would divert the attention.
Material
A good quality wood is highly advised, which is rectangular or square in shape. Having anything oval or round is not recommended, since it gets slightly tricky to organize stuffs on it. Avoid wrought iron table with glass top, since glass can divert the attention while making things beneath visible.
Few general tips are :
- Keeping the study, sleep, eating area separate.
- Keeping the study table clutter free
- Having the space well lit and ventilated
- Avoiding a window around the table to keep the concentration up
- Keeping the color of the wall pastel, Light blue or something similar to have a calm effect.