You'll be alright with the advice given on here. I just wanted to add that leaning a PA28 is a lot harder than a C172 which I've done a lot thanks to 40 hours of flying in Arizona. The friction on the lever, it's design, feel and the movement range makes the task practically impossible in some older PA-28 aircraft. You have to use two handles effectively. One hand as a safety guard against too much movement of the lever by the other hand. Otherwise it'll be oops,
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In the C172, you start rotating the knob anticlockwise at 3000ft, and simply adjust by a couple more rotations every 1000ft or so in the climb. Doing the opposite in the descent. So much more controlled and safer in a C172.