Keep the flaps up until over your chosen field. If you have tons of extra height, expend it in mini circuits while inspecting the field and approaches.
If there is any wind, downwind at slightly less than best glide speed gives you more choices and the option of doing a 180 into whatever looks acceptable.
Remember that a good approach to a poor field is much better than a poor approach to a good field.
Question: do you know how much altitude you will lose in a power off 360?
Once over the field, minimum sink speed is more appropriate than best glide as it gives you more think time. But as a glider pilot, I sometimes spend over half an hour "inspecting" a field before it turns out either that I have to land there or I find a thermal that gets me away.
For base and final, go back to at least approach speed and use flaps.
A good exercise is power off approach from the circuit. Bring the instructor along the first few times as he will remind you to have enough speed to flare with full flaps.