Hiking any of the larger trails in the US, will involve some hitchhiking. Normally, the trail will be crossing some lonely highway and you hitchhike 5-20 miles into the nearest town, and back, in order to resupply for the next stint.
Consider a sign
Some lightweight cloth or cardboard sign could prove useful, so indicate that you are not a homeless bum. “PCT hiker” or “not bums” will increase your changes of a lift. The people who live close to the trail and in certain “trail towns” are normally used to the hikers and will quickly pick you up, I never waited more than 20 minutes in more than dozen times I had to hitchhike. Put on a smile, stand up and clearly display your backpack and trekking poles next to you to show that you are a hiker.
It doesn’t look very convincing when 2 scruffy hikers are sitting on the ground with a lazy thumb out, even though their tiredness might be merited. All stand up, appear active and happy and don’t smoke.
Don’t be afraid to chat briefly with the driver about where he is going before getting in to his vehicle. Ask his name and if he knows the trail. And yes, there is some minor risk in hitchhiking, just like there is a risk in hiking and, well, in life. Being a cute, young, lonely girl adds to that equation so consider teaming up with a fellow hiker half-a-day before you get to a resupply hitchhike, in case you feel vulnerable.
Three scruffy looking male hikers in their 30s have a much smaller safety risk, but will also be waiting much longer for a lift, as many drivers will consider them a risk. If this is your social set-up, then consider teaming up with a female hiker to “balance out” your appearance and drastically reduce waiting time.