I have hitch hiked a couple of times.  Have you ever been hitchhiking?
I like asking strangers for a ride.
When did hitchhiking become commonplace?
I do not know, but I prefer the free rides vs the non free rides.
I agree with that!  Do you think it is dangerous to hitchhike in the present day?
As long as you use the proper hand signals you should be ok.
What are the proper hand signals?
You just extend your arm toward the road and stick your thump upward.
Oh yeah!  I know that one!  Is there any other etiquette that I should be aware of? 
I have no idea but there are very few places in the world that have laws to restrict it.