To me, the most repeatable way is using the RCBS precision mic for your specific caliber. I've tried the Hornady and didn't like it as much cause it moved around a bit.
The best way I've found is neck turning a case enough so there is approx .00025 neck tension on a dummy round. Enough neck tension to hold a bullet but the bullet can be pushed in with some pressure by hand.
Seat the bullet long and put a little imperial die wax on the ogive of the bullet. Insert in the chamber, cam over the bolt 1/2 way, carefully remove, and record the average measurement at the ogive. Repeat this until you get a consistent measurement. I keep that case and the same bullet set aside for checking throat erosion later.