If your using near field monitors (or any speakers for that matter) - try and keep them away from the walls and especially the corners of the room.

The reason is this: You get an effect called 'bass response' I think the technical term is. Basically due to the low frequencies being quite long wavelengths the reflections from the walls will be in quite similar phase and reinforce the bass part of your signal which could end up making you reduce the bass or over emphasise other components in the mix.

Hope this helps