The flare is the act of arresting the rate of descent which got you to the ground and slowing airspeed at the same time. It is possible to do a no flare landing (I watched a C 130 do one yesterday - Thump, and lots of blue smoke!), but don't do that in GA planes, they are just not built for it.
So you want to stop going down before you contact the runway. In a perfect world, you could have the aircraft aerodynamically stop going down at the moment you touched the main wheels, while holding the third wheel off. That's the perfect world, nice, but not always possible. So next, as Chuck suggests, flare, arrest the descent rate to zero, and pause so close to the surface (I like 6" high) that the plane could fall from there, and you'd still get a nice landing. As you pull nose up cautiously to hold at 6" high, the plane will inevitably slow, and thus settle gently on its own - hold that attitude! After the mains touch, hold that attitude! Eventually, the third wheel will come down on it's own nicely, while you control direction.
How do I know I'm 6" above the runway? On pavement, it's difficult. On long grass, I can hear and/or feel the tops of the grass whisping the wheels. In really long grass, you can feel the grass drag on the wheels. Look farther down the runway to judge height, not closer. It's not your eyes "measuring" the distance from the ground which is helping you to judge your height, but rather the "sight picture" which includes a whole lot of peripheral cues too. Your eye is judging the space between the plane of the ground (geometrical plane - not aeroplane) and the plane of your eyes. Your eyes are naturally conditioned to "see" in a horizontal plane, particularly while you walk, so you know which way is up. As you stand up, you see the two planes separate. When you sit down, your eye height perception tells you when your butt is going to hit the chair. Same thing once you calibrate your eye height to the wheels, your eyes will know when the wheels will touch. This does become a problem going from plane to plane with different eye heights. I'll fly both a floatplane amphibian (rather high) and flying boat (floats in the runway, not on it) in the same day, and eye height cues must be mentally supplemented!
Do not be in a hurry to get the flare over with! Think of it as a special, very pleasant experience of finite duration, and enjoy as long as you can. It has not ended when you touch, as you can still slow the plane aerodynamically while you hold it off while on the runway. And don't be in a rush to get on the ground to stop shorter. Even holding off in the flare, you're still slowing down, nearly as quickly as you would with a bit of braking.
Think of the flare as your final opportunity to get a little more flying for your money, just hold it off those last few seconds, and do not release the controls just because you touched. Fly it to the wheel chocks! (not vital for a 150/172/PA-28, but very good discipline for when you start to fly tailwheel!).