Lots of different opinions on this. Depends on kind of aeroplane and flying style too.
I tend to trim the airplane to fly straight and level at the flying speed used for the day.
In time for landing I trim the elevator for aproach speed and then adjust the descent rate with the throttle.
I find it easier to get the plane down this way, but it is only my personal opinion.
Guding a glider floating around I might use the trim almost as much as the sticks, again personal flying style.