My two favorite tutorials when learning about getting those corners done!
https://quiltwithmarcibaker.com/mite...s-the-point-2/
A technique for angles.
https://quiltwithmarcibaker.com/mite...iss-the-point/
I like to do a two stitch back tack and come back to the stitch off point. Use a ruler and mark the point of the stitch off.
If you are using a 3/8 inch seam allowance, mark the stitch off point at 3/8 inch also. For binding that is 2 1/2 inches wide, the 3/8 inch seam allowance gives a better fold line. The binding fold is more even between the front and back.