Having done lots of centuries helps because you KNOW you will be having those feelings, those thoughts, those cramps and tired legs. It doesn't take too many centuries to know that you shouldn't be hopping on the first pace line that comes by either. Knowing how to ride long climbs helps a lot too. But some of those "how to complete your first century" articles are just ridiculous - like working your way up to a 95 mile ride the week prior to the big event.