A couple of suggestions. These observations are based on my own experience doing a PPL. Talk these through with an instructor before you take them seriously...
1. Don't pick landmarks that will be directly underneath the aircraft. You may not be able to see them! 2-4 miles to the left side is ideal in a 172.
2. Flying the right heading is vital. IMHO Staying on heading to within a couple of degrees is more important than having a perfect crosswind calculation - randomly wandering 15 degrees either side of your course is worse than forgetting the -10 degree course correction.
3. Keeping track of time is just as vital - in fact being sure of time is *critical*. If you knew where you were 10 minutes ago and you have maintained a constant heading and know how long it should take you to reach your new destination you should be able to look out the window and see your landmark. Knowing which window it should be visible from helps.
4. Once you've done a couple of legs in the same direction you'll know what the winds aloft *really* are. At that point you can apply a correction using the 1 in 60 rule. Remember that you want to get back onto your planned course, not fly parallel to it.
theRolfe