Here is how our association teaches the mechanic, which matches what they do in MLB...
If the throw is coming from F7;
You go to the edge of the dirt circle, 3rd Base Line extended, and let the throw draw you in about 6 feet from the play.
If the throw is coming from F9;
You go to the edge of the dirt circle, 1st Base Line extended, and let the throw draw you in about 6 feet from the play.
If the throw is coming in from F8;
You decided which side of the center line the throw is coming from, and position accordingly, based on the two descriptions above.
Now personally, I think this is the worst mechanic in umpiring. It puts the catcher between the umpire an the play. Basically blocking your view. I have seen many partners working the plate, not see a missed tag or dropped ball in these positions. Especially 3rd Base Line extended.
For plays at the plate, I prefer the
Old School mechanic. Stand a few feet in Foul territory, far enough up the 3rd Base Line to see the Plate, and into the catcher. From here, you can see everything. I use the newer mechanics described above, EVEN THOUGH I HATE THEM, because I was dinged a couple of years ago during an evaluation for not using them.