The width of an average whitetail is 15" so if you can get a look at it coming straight at you or straight away that could be a judge. It only has to be a brief glance to get the idea if the spread is wider than the deer. Another method is the height of the rack. If the height of the rack is equal to the neck length (shoulder to base of skull) then it is a good size rack. I got those tips from a book on hunting by Clyde Ormond. It's and old book bought at a garage sale. Once you have been hunting several years it's like the post above, You know it when you see the deer. I must admit that you set the bar pretty high for a new hunter. Good luck and don't get discouraged it may take years to reach your goal