Signs

Hitchhikers often debate about weather to use a sign or not. If you decided to use one there are several important things:

• Think well about what place or text to put on it: take well known places, sometimes also road names can be used or more humoristic phrases ("I don't stink").
• Use the same font as the route directions
• Use contrasting colors: black on brown cardboard is not very good readable for passing drivers, black on white is far more readable

Tip: Make a sign of a large sheet of brightly colored paper glued to a sheet of cardboard. Cover this with self adhesive transparent book wrap. Now you made yourself a re-usable sign wich you can use with a whiteboard marker and clean again with a small towel.

When not to use

At big crowded gas stations where it's up to you to ask people, like in Germany on highway gas stations (and speaking fluent German). It's not very likely that holding a sign will actually be helping if you can already clearly state where you want to go and that you are hitchhiking.