First of all, you must have a stabilized descent. That means nailing your target airspeed and descent rate and maintaining them with very small pitch and power inputs. If you’re working hard at that part, ask you CFI to spend more time with you in slow flight. Without that stabilized descent you simply cannot develop any consistency when it gets to the end game of transitioning to the flare and touchdown.
I find that it often helps to think of the “flare” in two parts, the second of which is really the flaring part: “level off” and “flare”.
Leveling off involves flattening your downward motion – you transition the airplane from it’s descent to level flight. Thinking of it this way tends to help helps with ballooning problems since changing to the familiar level flight attitude tends to help avoid over-rotating. How high is the level off? Well, it’s usually somewhat lower, but you’re generally safe if you begin about a wing span off the ground – you want to level off into ground effect. The level off will start the process of bleeding off speed, and the final descent to the ground. Once it begins, you can start the flare.
The flare itself involves slowly (so you slow but do not stop the descent) bringing the nose up to the exact same position it was in when the mains left the ground on takeoff. I’ll repeat that. The flare itself involves slowly bringing the nose up to the exact same position it was in when the mains left the ground on takeoff. It’s easy to visualize and the best part is that if the nose is in that position, you will land mains first. (BTW, noticing my attitude when I take off is how I teach myself how to land an airplane type I never flew before).
Once you get the nose in that position, keep it there. Keeping it there will require you to continue to apply back pressure. It will also help you apply the correct amount of back pressure. I think that’s important to understand. CFIs constantly tell pilots to “hold it off” or continue pulling the yoke back. I know this is a standard instruction. I hear it all the time. It’s essentially correct, but I think it misses the point and leads to some very interesting ballooning as someone brings the stick all the way back because that’s the way it’s “supposed” to be done. But what happens when you bring the nose back to the takeoff position and do whatever is necessary to keep it there until it won’t stay up any more? Go back to slow flight. What happens? As the airplane gets slower, controls get less effective — more deflection is necessary to get the same effect. So you’re in the flare and getting slower and slower and slower. This means that in order to keep the nose in the same place, you need to pull back more and more and more. You don’t bring the yoke to your belly because that’s the way you’re =supposed to= do it, but rather it’s more or less the way you have to do it. If you do what is necessary to keep the same pitch attitude, you will be “holding it off”