A lot of good information.
I am a low action guy and I have a person who sets up my guitars with the lowest possible action. No buzzes. One of the first things he checks for is High and low frets. They may look good but if you use a straight edge, and it rocks back and forth no amount of nut cutting or saddle raising will stop the buzzing. So basically you want all of the frets to be the same height. THEN you can adjust nut, neck relief, and raise or lower the bridge.
I recently had a 400 dollar Vintage Gold top set up and he charged me 100 dollars for a fret level and set up. Now it plays like a dream with no buzzing.
If you get a steel ruler about 8 inches to a foot and put it on the fret board lengthwise you will be able to find and uneven frets. The first place to start with buzzes.