Install the tuners in the holes and tighten the top screws till their firm, but not super type. From there you can take a ruler, or flat edge of any type and lay it against the flat back part of the underside of the tuners and line them all up. I suppose you could be super anal and measure the distance from each and every tuner and make sure their equi-distant.
But then, once they're where you want them to be, you can drill the holes for the screws. Piece o' cake.