Is there a resource with tips to hitchhike?

As best as I can google, there are a few options out there.

Hitchwiki appears to be the most mentioned.

There is also RoadJunky for other resources.

I've hitchhiked a few quite different parts of the globe (Australia, Caucasus, East Asia, Eastern Europe, Southeast Asia, Turkey, Western Europe) so I think I've learned some tips and tricks.

• Many more people will stop if there's at least one female in your group.
• More people will stop for young people.
• The smaller your group is the more vehicles have space for you.
• Take lots of water. Murphy's Law of Hitchhiking states that it's always 40 degrees and the shade is always on the wrong side of the road.
• Expect to do a lot of walking. Be prepared to walk a lot. This is the hiking. Every hitch is a bonus.
• So don't take more than you can carry and wear comfortable appropriate clothes and footwear.
• Be as smiley and cheerful looking as you can. You are trying to get strangers to want to stop for you. Getting grumpy when you're not getting rides never makes people more likely to stop. Nobody owes you a ride.
• Expect to have to learn what works and doesn't work in each new country.
• If you are outgoing, go to places where lots of people are parked or out of their cars and ask them directly. (Rest areas, petrol stations).
• If you're in a country with a different way of writing and you're artistic, people will be very impressed if you can make a sign in their language. Draw the sign where people can watch you making it. Sometimes you'll have a ride before your sign is finished.
• It's easiest to get rides on large roads that connect cities. It's hardest to get rides inside a city.
• It's best to get dropped off on a road leading out of a city past the point where there will be any local traffic.
• It's worst to get dropped off at the entrance to a city or the middle of a city if it's not somewhere you want to visit. You will often have to find a way to get through to the other side of the city before getting the next long-distance ride.
• Find a place where people have to slow down or even stop. If it's legal, just past the tollgate onto a freeway/expressway is good.
• If it rains or you can't get a ride on the roadside, or you're not completely at the edge of the city yet, find a roadside cafe or truckstop, order something to eat or drink, set up your bags with your sign where everybody will see them.
• Don't try to aim for just certain kinds of people. Sometimes the cool kids won't stop and you will get rides from very poor people and very rich people. I've personally got rides on bicycles, buses, campervans, cars, minibuses, motorbikes, pickups, semis, taxis, trucks, tuk tuks, a BMW convertible, and a home-made cart pulled by donkey.
• If in doubt make sure the driver knows you are hitchhiking and not paying for rides. Usually drivers that want money look "different" or talk about money as soon as they stop. Occasionally an innocent misunderstanding might lead to a ride with a driver asking for money. So try to make sure as early as possible they understand what hitchhiking is or that you have no money. Pidgin English "No money OK?" often works.
• If people don't understand the word or concept "hitchhike" try words like "adventure" and "challenge". Especially people that want to drive you to the bus station.

These are some of the techniques. Some of them look obvious when you read them but it cost me a few hours waiting to learn. These only reflects my experience as an ocasional hitchhiker and may not perform well in every situation.

• Avoid curves (drivers don't like to stop near curves - it's dangerous to stop due to low visibility). The curve can also hide the hitch hiker. That means the driver only sees the person too late and can't prepare to stop.
• Avoid hitch hiking right after the top of a hill for the same reason. The driver will probably see you only when getting to the top meaning he doesn't have much space to stop. There is also low visibility if someone is coming from behind.
• Avoid roads going up (drivers, especially truck drivers hate having to start in an incline - it takes a lot of energy for a loaded truck to start in such a way - plus it's a very slow start)
• It's a lot easier to get a hitch hike near locations (cities, villages, etc.). I think drivers are more suspicious about people "lost" in the middle of "nothing". Might be better to refuse a ride that leaves you in the middle of nowhere (this has to be evaluated on the spot, sometimes one can't just refuse).
• Look the driver in the eyes when you hitch hike. Try to make visual contact.
• Find a place with space for the car or truck to stop. This is especially important on busy roads.
• Avoid road segments where cars pass at very high speed. Usually city/village exits are good spots. Cars are still driving at low speed and it's probably not local traffic.
• Avoid being left or start hitch hiking in very low traffic roads (eg. < 3 cars/hour)
• Don't just accept any ride. Think if the place where they leave you is good considering all the previous tips. Then again, this needs to be judged on the spot. Sometimes one can't just refuse.
• The probability of a driver stopping is inversely proportional to the size of the group