(not mini golf)
lol
As was already mentioned, make sure everything is in alignment: toes, knees, hips, shoulders, and eyes. Try to get your eyes right over the putting line.
Next, use the big muscles of the back and shoulders to strike the ball. Don’t get your wrists or hands involved in the stroke.
You might also try different gripping methods like left-hand low or the claw.
During practice, try putting while looking at the hole, not the ball.
Make sure the stroke makes the ball roll end over end without skipping.