Similar technique to others by my instructor.
1 - Pull up 3/4m or '3 mirror widths' (theirs, yours, and a same sized gap) away, and with the front of their bonnet in your front passenger side window.
2 - Reverse beck slowly until the rear corner of their car is in the rear quarterlight window and turn 1 full turn left (not full lock).
3 - When the same rear corner of their car is in the middle of the passenger side window, turn one full turn right.
4 - When the edge of my left door mirror lines up with the middle of their car, one full turn right.
5 - Straighten with one full turn left when it feel straight.
Worked a treat in his car, and I could easily adapt it for any car I drove until my spatial awareness negated the need for reference points.