Once the concrete has hardened and we can walk on it, I can think about the positioning of the lights. I'll be using standard 50 Watt spots, mounted in the plasterboard ceiling, and the cabling has to be in place before the plasterboard goes up. Julian, my brother-in-law, has put up spots in their kitchen and I asked his advice on spacing, etc.
There are two beams in the kitchen, and in the gaps they create I've planned for three rows of spots, with 3-2-3 lights to the rows, to get an even light distribution. I found it remarkably difficult to get everything in the right place. Lines that were supposed to be straight were not, and I was up and down the ladder like a yo-yo correcting this or that error. In the end I think I got it OK. The wires are laid out where they are supposed to be, and the spot positions are marked with string hanging down.
And since it's a good idea with electrical things, to check it as you go along, I suspended a bulb from time to time to check that all was well.