Always secure your lights/ballasts off the floor with not just one set of supports, but also a safety chain connected to something sturdy in case of failure.
Ground all circuits and put CFI outlets in if possible
If you have something that draws 18 amps, put it on a 20A breaker by itself.
Always allow for surges! Overloaded circuits are VERY dangerous.
Check the max amperage of your timers too. Most grounded timers you see at home depot etc only allow 18A. You will REALLY want an industrial metal-housed time clock for a grow over 1000w.
I had an electrician come in and do my grow room on 2 dedicated circuits... one on a timeclock for the lights-on systems in flower, one not for the veg area and climate control.
Never a problem.