There is a useful technique to trimming...
Power
Attitude
Trim
For example, you have just taken off from an airfield and you are climbing away. You will have your power set. You then need to set your attitude to get a good climb speed (75KIAS is good in a Cessna). You then need to hold that attitude to get a feel for what the aircraft wants to do. If it wants to pitch down, add some nose up trim and vice versa. It is that holding of the controls to work out what trim you need and how much trim you need that will save you the pain of a bumpy journey.
When coming out of the climb and levelling off:
Attitude
Power
Trim
You need to adjust your attitude to maintain level flight. You then need to readjust the power to a cruise setting. You then need to hold the controls required to maintain straight and level and you can then trim out any forces you are having to hold yourself.
Never try and fly the aircraft's pitch axis using trim - you'll end up with a horrible sine wave flight.