My advice as a CFI is to pick waypoints that:
1) Readily identifiable and distinct when viewed from all directions. Many people select waypoints like small airports, country roads, etc without really being awareness of how easy these are going to be to spot from the air. Good waypoints are natural things like oxbow lakes or bends along a river, tips of finger lakes, small buttes, small lakes or ponds. Many man made features are excellent references like power plants, freeway interchanges, concrete plants, substations, sport stadiums, pit mines, small isolated towns in the countryside, prisons, large bridges, water towers, dams, etc. Major airports may be used but I’d refrain from using small, country airports as they are often very difficult to pick out from the countryside if you are unfamiliar with the area. In addition, I like to review satellite photos using Google Earth, etc over the proposed route and see if all my selected points are readily identifiable.
2) For whatever visual waypoint you choose, make sure there are other visual references nearby which you can orient yourself to to locate your position relative to your chosen waypoint. For example, you’re flying towards a bridge which is your chosen waypoint and you spot a finger lake a mile or so directly to the left of the bridge. You can use this to determine when you have crossed your chosen waypoint by noting when the finger lake is directly off your wingtip and you were tracking directly toward the bridge.
The 3D trip simulator in ForeFlight is an excellent way to do a practice fly through of a proposed CC route and make sure you can easily spot all your waypoints and visual references.
3) If you’re flying an airplane with conventional instruments and a free gyro heading indicator BE SURE TO A) ALIGN THE HEADING INDICATOR TO YOUR MAG COMPASS BEFORE BEGINNING YOUR TAKEOFF ROLL AND B) PERIODICALLY RE-ALIGN THE HEADING INDICATOR WITH THE MAG COMPASS EVERY 15 MINUTES WHILE ENROUTE WITH THE AIRCRAFT IN STRAIGHT AND LEVEL FLIGHT. You wouldn’t believe the number of solo CC students who depart on a flight and head off into the boonies because the completely forget to do this!
4) Be in a position to get a good view of your waypoints. I personally prefer to select a VFR cruise altitude of between 4000-5000 ft AGL, obstacle clearance and aircraft performance permitting. This provides a good ‘perch’ for navigating by pilotage, high enough that ground clutter can’t obscure your view, but not so high that it becomes difficult to spot visual details.
5) Never select visual waypoints more than 20NM apart. This will help to both minimize wind drift errors and corrections and 2) keeps you relatively local in the event you really do get lost and require ATC assistance to locate your craft.
6) Get the latest winds aloft forecasts and re-compute your magnetic headings, preferably less than 1 hour before your scheduled departure. This should help minimize wind drift errors.
7) Log all of your times on each enroute segment and compare these to your ETE for each segment. Note any differences in your position relative to your waypoint and update your actual winds aloft using an E6B periodically.
8) In the movie The Patriot, Mel Gibson’s character advises his son that to shoot a gun accurately, he must aim small so as to miss small. This is very good advice for good cross country navigation as well. Make a deliberate effort to fly good straight and level segments with as minimal deviation from one’s desired magnetic heading as possible. The best way to do so is once on course, pick a reference point in the distance eg a distinct farm field, a cloud, etc and just hold the nose on that point with very tiny aileron inputs. This will minimize course tracking errors.
9) You can periodically identify your position using two VORs to get a fix. Verify you are still on course and where you intended to be when you intended to be. NOTE: Be sure to identify each VOR with the Morse Code tone to verify that they are working properly!
10) Finally if you do actually get lost, remember to use the 6Cs - CLIMB, CIRCLE, CONSERVE, CALL, CONFESS, COMPLY to find your way back to your destination.