Make sure there is easy access to the tank, and especially for feeding. Also make sure you can ventilate for heat, especially with MH lighting (if you have MH!). I am planning a new hood for my 135, and I plan to have it hang above the tank so it will not hold in heat that will transfer to the water. That will also make it easier to raise and lower the lights over the tank if I want to decrease or increase intesity on the tank. Drawbacks to doing this: there will be increased evaporation, and there might be more light spilled out into the room than with a completely enclosed hood.
Make sure the parts that are near the water are waterproof. You can paint it with epoxy paint, or cover it with plexiglass.
Good luck.
Sonny