“If you can’t locate the bridge you will never get across the river”.
Actually, the key is knowing where the bridge must be placed, hence you will know it’s location. All guitars have what is called ‘scale length’. This ‘length’ is the distance from the front of the nut to the top of the saddle,(saddle is mounted in the bridge hence the ‘bridge’ location sets the saddle location. The mid point of this scale, 12th fret, must be the exact distance from the saddle as it is from the nut. Once the neck is permanently in place and the nut is installed, a simple tool, (saddlematic at Stewmac), to measure the distance from the nut to the 12th fret, then flipped 180 degrees to locate the bridge utilizing indicator pins for correct compensation for string deflection. This is a very critical dimension and requires double-double checking before drilling bridge pin holes. I will always lay this out and make light pencil marks at two corners of the bridge, then I repeat and check my marks. If it looks a little different I’ll mark the other two corners then recheck ’til I am satisfied. Now carefully clamp the bridge in place and drill 3/16″ through the top and the bridge at the ‘A’ and ‘B’ string holes. When ready to glue place the bridge onto the location using short 3/16″ dowel pushed down flush with top of bridge, then clamp with bridge caul and bridge plate caul. That’s it. Once you remove the clamp, re-check the location of the saddle. Remember that it is always an option to remove the bridge and start over if it moved. Keep smiling and move on.