From randonneuring experience:
Standard correct answer: Follow a cue sheet
What really happens a lot: Follow the herd because Pam up there has a GPS.
OR, you've ridden that route 8 times before and pretty well have it memorized.
If the route is especially bad or confusing, try to follow the ride through in detail on Google maps or RideWithGPS beforehand. (Quite likely, somebody has already entered it on RideWithGPS, so try a search for it.)