I usually look for the antlers to be at or past the ear tips, as cardeer said youll be looking at about 16 inches. I also look for at least 8 points, and the g-1s to be 3 or more inches, and g2s to be maybe 8 inches, with these sizes and some decent mass, you are probably looking at a deer in the 120s. If you see all of these or more on a deer, it is probably a shooter for most guys with a bow, unless they are in a really good spot where they know there is better. Its just something you have to look at lots of racks and get some ideas of general rack size and more inportantle "frame" size, I generally look at the frame of the rack than the number of points. Try to attend some deer hunting expos or somewhere you can look at lots of deer of all sizes, and get an idea of what you would consider a shooter. Hope this helped.