Everybody knows about items' sweet spots (each item has a favored spot on the where-to-chop-slider (or, "you sense Iron Ore exactly where you are swinging")) but there are less-obvious inputs which items favor. The first is the remainder bar. There are four possible lengths of the starting remainder bar, and each item consistently uses the same one. So, if you're at Iron Lake, and you start mining, and the remainder bar is at placement B, then you know that you're about to dig up some cobalt ore.
The second consistent input for each item is the strike zone. Logging uses five zones, and mining uses four. The images show good places to strike to hit each zone. Cobalt ore's strike zone is 4. So, if you're mining at Iron Lake, and the remainder bar is at placement B, then you know that you merely need to strike at zone 4 to dig up your cobalt ore.
I made a tool that gives you this information about each item.
Here it is.
You can pull up the tool for each camp. Ideally using these tables will let you know what you will dig up/chop down before you even strike.
Note: In order for the strike zone to be consistent, you must be high enough level and have adequate amounts in the appropriate stat (Botany STR, Mining VIT). When you don't meet these requirements, the item may be placed into a random zone.
Lastly, thanks goes out to Aviha Chai from Fabul for gathering all the remainders, strike zones, and max yields for every logged/mined/quarried/harvested item in the game!