The best tips I can give you are:
1. Pick LARGE (easy to see from far away) items as your waypoints. Lakes and large towns are good. Small villages are bad, as it's often difficult to tell if it's a village or a small collection of houses.
If you are a few miles off track, a small village is impossible to identify. A large town or lake is much easier to see from a few miles away.
2. Don't fly directly to each waypoint, but instead fly a straight line. Ie. if you have waypoint A, B and C, which are pretty much in a straight line, but flying directly over B on the way to see, means your heading changes by 5 degrees, then forgot it. Fly a straight line from A to C, and have B waypoint as "2 miles north of B". Less heading changes means less chance to get it wrong, and easier to apply drift correction.
3. Have your waypoints further apart.
When I was training I was thought to have waypoints about 10 minutes apart, but later, I found that this actually left me in the position of constantly trying to fix my position (and using smaller waypoint such as small villages). I felt over worked, as I was constantly trying to see the next waypoint ahead.
Much easier is if the waypoints are 15-20 minutes apart. Then in between do the following:
From the start of each leg, mark off where you should be on the map every five minutes into that leg. Eg. 5 mins, 10 mins, 15 mins after point a, then start again 5 mins, 10 mins etc after point B etc. Now you have 'little waypoints' to help settle your mind about where you are, but you don't have to spend time writing up your plog and adjusting estimates, and working out new drift correction, and closing angles. Instead you can simply look and think "yep....things are working out nicely, and I know exactly where I am...now lets see how much off course/time I will be when I get to the next actual waypoint" (Which might still be 15 mins away). Less mental stress.
Point three is a bit of over kill, but I found it very useful when I was lacking confidence in navigation. When you become more comfortable, you won't need it.
I hope that helps.