We all have to nail , screw any bracket or fixture now and then on walls or somewhere. It is quiet a hassle when it comes to drilling the hole in wall.
A quick shake of hand or bad judgment and you have a hole which is not on target.
I have seen a slick solution of this everyday problem on American Wood Worker's site.
First scan the equipment you need to drill holes for. Now print that scanned image on 8 1/2 x11 paper. Photocopy also work fine.
Now fix the printout on wall via tape and now you have exact location where you need to hole / drill.