Having the correct grip when putting can effectively improve your overall stroke almost immediately and quickly get you on the road to making more putts. The photo shows what I call the 'trigger finger'. Have all 9 of your fingers touching the grip itself with no overlapping or interlocking. Simply extend your right index finger straight down so the finger tip rests on the left index finger nail. This finger tip to finger nail will feel similar to squeezing the trigger on a gun.
This grip not only blends your 2 hands together put keeps the right hand and wrist firm throughout the stroke, eliminating any wrists which is vital to good putting. Most tour pros use this and I think it's the best putting grip out there