Almost everything you need is already somewhere on this board. To answer your question though, you want the light as close to the plants as you can get without burning them. A simple (but imperfect) way to do it is to put your hand under your light. At the distance your hand can stay comfortable under without heating up too much is safe for the plants, but ideally you want the plants to be in an air temperature under 84 degrees. If you are sealing the light and cooling it using forced air, you will get the light alot closer to the plants then if you aren't. I am running a 1000 right now over my plants and have it approximately 36 inches above. Once I get my vortex fan I will be able to seal the enclosure and move it much closer. Hope this helps. Also check out the website:

http://www.drugs-forum.com/growfaq/G...c%20Topics.htm

That has a lot of the information for the deceased overgrow website, which should be able to answer most questions you have. Good luck.