I recommend just buying a pre-made aquarium light hood that just sits on the tank.
But I have made my own and attached them to a wooden hood. I got 5 magnetic ballasts (~$9ea??), 5 starters (50c or something), 5 sprung loaded endcaps ($3?), 5 normal end caps ($3?), some thin wire ($10), some mains cable ($10) and a plug ($15) plus the 5 tubes ($7ea) and wired it all together. Goes great, and was much cheaper than buying pre-made units, but if you're not good with mains powered electronics, best to avoid it.
Got the bits at a local electronics wholesaler.
I will be DIYing a few more, just because I can't afford premade units and I've got another planted tank to setup in a few months. But next time I"ll go for those waterproof endcaps with the flying leads, and I'll try to get electronic ballasts which are much better.