It's no different than laying out railings so the spindles come out even all around, or ceiling tiles so they come out even all around, etc...just do yourself a big favor and buy a few cans of aqua net so after you snap the lines you spray over them with the hair spray so they dont "get lost"
It takes a lil time to layout/snap'em but once it's done you can fly, I'll have one of the guys 5-8 tiles ahead of me cutting the funny area's that eat up time so when i'm laying/setting the tile i dont have to wait, it's just constant motion until completion. But, but often you will obviously have to use your better judgement, there's been countless jobs that after measuring it out we'd have the end pieces being some ridiculously small sliver, so we'd end up shifting the entire grid over so we could fit an almost full tile at the perimeters. I'm fix'n to walk out the door, so hopefully somebody today can explain the math, it's very easy since all your doing is dividing the space by tile size, finding center of the room and then doing layout from there.