What's the best/appropriate way to adjust paralax?Pick a target and keep dialing the objective 'till it's clear?I know the numbers on dial are just a guideline.
"Just a guide" , it depends. The range numbers on a Leupold objective are very close, right out of the box.
The adjustment ring distance numbers can be "adjusted" on most quality scope. For example get your parallax to zero (no parallax) at 100 yards and then loosen the lock screws and rotate the numbered ring to read 100. This will allow use of a range finder and quick turn of the scope.
If hunting larger size game. Like deer, set the parallax to 150 yards and forget about.
Parallax is a big problem at close range. Close range and higher magnification. A good example where parallax can bite you is shooting squirrel at 10 yards to 100 yards with 12x scope.
Looking for a sharp focus IS NOT ADEQUATE. The only test that works for me is to secure the rifle very steady and move my head side to side and see if the point of aim moves.
A good rifleman will hold his head in the same position with every shot. If you can do that parallax becomes a very minor consideration for a very minuscule percentage of shooting activity.