slight split grip, right hand predominant for speed, back of left hand squared on the putting line. open stance. The faster the greens, the more I try to get vertical/pendulum with the putter. Left shoulder raised, low takeaway to promote upward strike.
For speed I will watch other putts and rolls and try and calculate how far it will go and compare the actual resort. Use feet for slope. Would prefer to be tending the pin as that helps in reading. Note the color of the grass for slope and grain.
For those of you who read Golf Digest's speed putter article I agree with the caveman theory.
When looking over a putt I will try and find a blemish and watch my virtual putt. If it breaks below the hole I will adjust for more break and continue to make virtual putts until satisfied. Knowing that the hole is 2+ balls wide my putt's finishing position should be less than a foot past and on the low side of the break.
When playing with a caddy I prefer to read my putt, tell the caddy what I see, if there is no agreement will discuss to find out what I am not picking up on the green.
Years ago I decided to try side saddle and after considerable practice was very happy. On the first hole I had a 4 ft birdie putt and didn't hit the hole on the first two putts.