Symbols, like all other forms of magick, exist and work because we believe they work. Draw a symbol you think is good for the purpose you require it and as you draw it visualize your energy going into it. As your energy flows into the symbol, visualize the energy programming it for your cause. When you are done what you do is up to you, some people like a little finishing ritual and some people just leave it be.
If your imagination fails you, as often happens with people after hard days of work, you can look up symbols online. Japanese/Chinese symbols, runes, etc.