For me a loupe or a microscope helps with this but only because I know what to look for. Even so honing scratches can make assessment tricky unless you look at things from a number of angles . Some use thumb pad or nail tests. All are useful & used in combination even better.
Experience & 'screwing up' will teach you a lot. ;)
Look around for pics on SRP if you area visual learner.
Link below shows some diffrences between incomplete & complete bevel.
http://straightrazorpalace.com/advan...tml#post892889