If you go to any search engine and type in "Beef Cattle Selection", etc. you will come up with very good information from professors, etc. Also, if you want you could look up example classes so you can see how well you can place animals that have official placings. I saw the Belted Galloways at the Hoosier Beef Congress and, while I'm not to familiar with the quality of that breed, they looked less than ideal. I'm sure there's good Belted Galloway cattle though.
Your association should have a "Breed Standard" usually with a photo showing the cow/bull that closest fits the standards. Try & buy your foundation animals that come as close to the standard as possible
This is my Highland cow that I use as a base I think she fits the breed standard pretty well
This is my bull, again when I purchased him I tried to find a bull that fitted the breed standard for bulls
Good feet(walking on their toes, not their heels) Good thick legs-it is acceptable for the Galloways to have "short" looking legs. Nice udder, not too saggy, but not so tight to her that it's impossible to find. Good teats, not too large or long, but not too short and small. With the Belties look for a full belt, to help with registration, but incomplete belts are acceptable for registration as well. If you need information on breeders, PM and I can get some information for you. Also with the Belties, they are Galloways, so they should be fairly docile, not crazy and trying to run you over and charge you, regardless of if they have been range cattle or not. Straight backs are VERY important as well.