Note: Commenting fixed
Thumbing a ride was already considered low class by my teen years. Not too long before, servicemen regularly hitched rides and no one thought the less of them for it, but by the late 60's, middle class parents had the double horror of both danger and "looking like some bum" regarding hitchhiking. College students, especially those of a hippie bent, still engaged in it, and it was almost required of actual hippies. Unless you had a VW of course, in which case it was your duty to pick up hitchhikers. Additionally (though overlappingly), lowlifes of various sorts also hitched.
In the context of another story I recalled my hitching back and forth from Virginia to Massachusetts during college, remembering something of the practical knowledge one simply acquired by experience and word of mouth. Distance hitchhiking was different from thumbing to work or within your own region. Different strategies, different rules. Locally, you could display some easily-recognised identifier that you were a counselor at a local camp, attended a local college, or worked at one of the ski areas or local tourist venues. Hikers in the White Mountains still hitchhike back to their cars and locals pick them up. Such identifications improved your chances of getting a ride, as they were a reassurance.
For traveling any distance, there were decisions to be made about appearance and especially signs. Pieces of cardboard had two sides, and you wanted the best two destinations out as choices. If you were trying to get out to the interstate, your sign that said "Boston" might actually be a put-off in rural Virginia. You needed over 600 miles in all, but the first fifty and the last fifty were often the hardest. Like the train, actually. Locals wouldn't figure that their ten-mile lift was going to help you much, so they wouldn't bother. And you were a damn Yankee college student, probably a faggot from William and Mary anyway. "I-95" would work better. But that wouldn't do you much good once you got to Richmond and I-95, would it?
Once on I-95 you had two pools of potential lifts, and a different sign would work for each, so you just took your chances. "Boston" was a place people recognised as a long way off and up north, even if they had only the vaguest idea where it actually was, so you could get rides that told you "I can get you to the other side of DC," which was great. Progress over a hundred miles was always good news.
But even "Boston" could put you out of the running for a really solve-all-your-problems ride to eastern Massachusetts, because there were folks who would stop for someone closer to their actual town, like Sudbury or Newton, but not for a generic "Boston," because then you could be from just anywhere. Lawrence or Revere or something else unseemly. But if your sign said "Sudbury," nobody in Maryland knew where the heck that was and would drive on.
There were people who would pick up anyone, even if they were only taking you a few miles on, just for pity or for company - or some annoying pathology of their own. And it was standard knowledge that girls got rides more easily - because of pity, company, or pathology - so having a girl along was an advantage. Or so I'd heard. None of my female friends were hitchhikers, except for the one shyest, most overprotected girl, who hitchhiked all summer the mile back and forth to the beach where her family vacationed. I still can't picture that, really. Whole 'nother story. Regarding female hitchhikers in general, I only rode with them when some magical person would stop and pick up a whole slew of people standing at an exit.
It offended my sense of honesty, but I found that a sign reading "New Hampshire" worked better, even when I was actually going to Massachusetts. I was actually from NH and identified more with it - my family had moved to MA right after my highschool graduation and I had few ties to Sudbury. Twice in the four years I got a long ride from someone who ordinarily didn't pick up hitchers, but saw that NH sign and figured I must be all right. Wanted to know right away exactly where I was from and both times, we identified people we knew in common quickly. (Even then I knew people from all over the state and remembered their geography.) One ride from outside Wilmington, and one in north Jersey. Our tribal instincts kicking in again. I went more than an hour with both before I confessed I really wasn't going all the way to NH. And heck, if they had somehow signaled that it was important, a ride from Wilmington to Manchester would have been great and I would just have kept my mouth shut.
Still lots of stories to go about thumbing, but I don't think I'll tell them. The psychology of signs was really all I wanted to cover.