[ProDigit]

I've always listened to techno or trance. The soft background melodies that repeat itself are an excellent way for the brain timer to shut itself off.
If you don't have these kinds of music, just turn on a room fan, or something with a constant pitch or whine that the brain will shut out.

Provide the brain with all the nutrients it needs. Milk and honey are good nutrients!
Spagetti is a great food to eat before studying.

A short catnap before study can do miracles as well, as it clears memory, and synopses are most sensitive 30 min to 1 hour after waking up!

There is some study done with magnetism, exposing the brain to strong magnetic waves, could temporarily disable one part of the brain, making more focus for the other parts. This is experimental, and could lead to all kinds of deseases like cancer or possibly even a brain short; where synapsis get burned or a connection made between 2 synapsis that don't need the connection.

I would not recommend the latter step though...