low n' slow
Everyone has their own opinion, and experiences, on this one, so here are mine!......
Start the flare at about 20ft above the runway, and at this stage transfer your gaze to the end of the runway. As to power reduction, there are as many views as pieces of string(?) and the timing, extent of this varies from instructor to instructor. It won't have much effect on the final touchdown in a 172. So far, I am sure you are yawning. It is from this point on that I may be able to help.
OK, now for my experiences and opinion.
Firstly, when a C172 is going slow enough in the hold-off phase to make a slow touchdown (and the stick is right back, or nearly so), you CAN'T see over the nose, and therefore can't see the end of the runway. The situation is much worse in a C152. Looking over the nose after the initial flare will usually result in a three point landing, because you will stop pulling back on the control column when the end of the runway disappears! Also, you have now lost all depth perception.
So, what to do?
Where I was taught, the method was to stop looking at the end of the runway after the initial flare and the hold off begins. Look now about 30m ahead,and to one side of the cowling. One instructor used to push the student's head against the side window by way of encouragement (and none too gently either)! You will find that you have excellent depth perception, and can stay straight as your peripheral vision tells you if need any correction to stay straight.
With this method, you will find you can keep the aeroplane flying along quite nicely, just above the runway, until the stick is right back, and she will just settle down when she is ready, at a nice slow speed (with the stall warner just going). The end of the runway disappeared from view long ago!! Remember to get that head off to one side!
When I was doing my PPL my landings left something to be desired - until the CFI did a few circuits with me. We landed and he went and stood about 30m in front, and to one side of the aircraft. He got another instructor to push down on the fuselage, so that the nosewheel came off the ground and the view ahead was obscured by the cowling, just as happens in the hold off. He simply asked: "Can you see my feet?" I couldn't. Cushion inserted, and I could. Problem solved. I could previously see to one side in the flare, but only about 10m ahead so everything was too close and a blur. The seat was semi collapsed!
I'm not that short, about 5' 11" (1.80m) (6ft to the girls), but the cushion just revolutionised my landings and I never looked back. You can usually adjust the C172 seat upwards, but a battered filling can lose you 2-3" of height, and this may be all you need.
So, in summary, two suggestions.
1. DO NOT look at the end of the runway during the hold-off.
2. Get a friend to try the tail push-down test for you, and use a cushion if you think it might help.