Hey Gerg, gas stations, brushed teeth, and clean hands. That's where it's at if you're hitchhiking on interstate. I find standing on a freeway entrance with a cardboard sign and my thumb takes forever, people don't know what to think about the person as they're passing by and they don't have enough time to think about it. Here's how you solve this problem: Go to a gas station, use the bathroom, brush your teeth, take a little bird bath, wash your hands, make yourself decently presentable and smelly enough to not stink up a closed car. Then you get yourself a snack or whatever, and go hangout on a curb that has a good view of the pumps. Now in order for this to work well, you need to be at the gas station that is next to the entrance ramp you want. If the entrance ramp is a complicated 4-leaf clover curly q loopdy doo, then it's going to be more difficult, but still easier than putting out a thumb.
This is the trick, you catch the driver before they start driving, the gas station is perfect for that. Some drivers are heading in one direction and will pull off the freeway, fill up, and hop back on the freeway, approach them politely and ask them if they're heading south on I-5 (that's an example). If you're on the north side of a big city, chances are they will be going south, but not far, you want to be on the south side of that big city, you can accept that ride into downtown, but don't expect to hitch out, you'll have to walk or take transit or subway or whatever. If you're on the south side of said big city, your chances of getting a ride go way up. If you're somewhat clean, it's polite and that shows that you are considerate and smart. If you're pleasant in asking for a ride, you can get a ride super quick. I figured this method out on my own after standing near freeway entrances for hours and having plenty of time to think.
I've stood next to freeways for hours with a thumb, a cardboard sign and more patience than I knew I had, sometimes that didn't get me anywhere while the sun's starting to set. I eventually figured out to just walk up to the gas station and ask for a ride. The first time I did this, I got a ride from the first person I talked to and they actually offered me a ride all the way around the country (I declined the distance and went half way across the state with them). This has worked wonders for me on freeways where hitchhiking is actually illegal. This is my little loophole and I'm very proud of it. If you use this, please be nice to your ride.
One time, I got a ride out of a 4-leaf clover freeway entrance after getting kicked out of the closest gas station. I stood on the sidewalk next to a stop light intersection and held up a thumb and started calling out to the cars that had windows down "Yo! We need a ride south!". There was a lady with me and we were standing just before this guy who was flying a sign at that intersection (we were there first). Once I started calling out to traffic it took about 5 minutes to get a ride. It didn't take us far which is okay, but it got us out of that terrible intersection and back to the regular style freeway ramps with gas stations right next to them. From there, hitching got easier, but still required a bit of ingenuity. During that trip, we had been dropped off at a gas station next to a freeway entrance where a hitchhiker was standing with his thumb and a sign. The lady and I, drank a tall beer and got some free food and were hanging out while watching that hitchhiker, a camper pulled over for him and he turned that ride down. When we were ready to go, I approached a car, asked if he was heading south on I-5 and if we could get a ride. His answer was yes and yes. We passed that hitchhiker and I realized the benefit of being creative and clever, also listening to the drivers as you're hitchhiking is more important than some would think. If drivers are pointing at something as they pass you by, figure out what they're trying to tell you. Just as hitchhikers communicate with their hands, so will drivers. Be receptive and listen, doing this will allow the universe to direct you to the path of least resistance.