Taken from Wikipedia:
Green in regulation (GIR) A green is considered hit "in regulation" if any part of the ball is touching the putting surface while the number of strokes taken is at least two fewer than par (i.e., by the first stroke on a par 3, the second stroke on a par 4, or the third stroke on a par 5).
Basically, if you can Eagle or Birdie on the next shot after you safely drop your ball on the green, then you are "in regulation". You do not need to have 100% Fairways (FIR) to get 100% GIR.
Do that on every hole on an official course. Obviously, this will be easier if you play a Custom game, turn off the wind, make the weather Clear, play from the closest tees, and play on Easy.
What else should I add? Please make a comment if you can add valuable info.