I found that if you visit every taxidermist you can find and measure some mounted heads, it's very helpful.
This is what I made up for myself: First, look at the fronts. You want at least two browtines to extend the measurement of the palm. Second, look at the length of the palms. This is best done from the side. A great bull's palms will just about appear to sit over the shoulder hump. Width of palms is next, I found that bull's ears are about 10" long. If the palm looks as wide as one ear length, it's a keeper. Lastly, I found that bulls at alert are roughly the same width as a mulie- 22-24 inches. IF you can see daylight between ear and antler, give it 2 inches per side. If you think the palm is and earlength wide, you have 10 inches per side.
This gets you pretty darn close to a 50 inch moose, which is darn big by Shiras standards.
My bull was only 39" wide, but he scored very well due to browtines, length and width of palms.
Hope this helps rather than confuses.
Pred