Soft-field T/O:
You start with full backpressure and release some as the elevator gains effectiveness due to airspeed. Once you feel the wheels release from the ground, just level off. You don't need to look inside, just move the yoke forward until the ground doesn't get nearer or further away. And just maintain runway centerline. Begin a climb at Vy once you reach it by adding some backpressure. Remember that the airplane wants to get off the ground, you don't have to help it. You just need to make sure it doesn't leave ground effect.
Soft-field LDG:
When you get into ground effect 20-30 feet above the runway level off a little and reduce power to control the sink rate. Smooth reduction of power will allow you to settle nicely on the runway. Landing point isn't a consideration, but you don't want to float halfway down the runway either.
Short-field LDG:
Make sure you're using full flaps on landing (unless it's really windy) and get to your slowest airspeed right at and above your target point. Since you're flying a PA-28, when you pull the power out, the plane will descend (aerodynamics of a brick). Use that to your advantage. Reducing power will increase sink rate (to land within the target), adding power will slow descent rate (so you don't land early).