Lumens are an iffy measurement of light for plants. The lumen is a unit that's derived from light that the human eye can see, and not necessarily the light that plants use for photosynthesis (which is not only widely different than what the eye can see, but also varies from plant to plant IIRC.) So light sources with the same lumen rating can vary widely in their usefulness for growing. Generally, I try to use four or six four-foot, 40W T12 tubes at a bare minimum, which I think adds up to 8,000-18,000 lumens (approximately.) More critical is understanding that the lights need to be close to the plants; the concentration of light at a given distance from the source is governed by the inverse square law, which in a nutshell means that the amount of light diminishes exponentially as you move away from the source.
Hanging most T12 fixtures from this type of rack is simple. Just use some S-hooks and short lengths of chain. The lights have holes in the casing where an S-hook fits, and the other end of the chain is connected to a shelf above. I like to use the margins of the shelves rather than the part that stuff rests on, to avoid accidental bumping. I've never had a tube break, but I have had a couple close calls where fixtures fell. Hanging wide fixtures can be more tricky - for instance, I have some six-tube T5HO fixtures that are too wide to fit between the legs of my racks, so I have to hang them on diagonals to fit. But the same principle applies - I just use brackets and S-hooks and hang them to the shelf above. (Or sometimes, because the T5 fixtures have hoods that cover the tubes completely, I'll rest the fixture on a shelf above. This makes me feel a little more secure about the possibility of a fall.)
This thread is so handy, it really deserves some pics now that Darcie isn't around... next time I rearrange shelves I'll try to get some good step-by-step shots.