The amount you will pay per click varies a lot. They have an automated keyword generator, that if you put in a keyword, it will not only tell you how many times that keyword was searched on last month, but will give you a list of related keywords, and how many times they were searched on. Don't be afraid to bid the less popular keywords - remember that you can get placed much higher in those keywords for very little money, and so will get a large ratio of clickthroughs for those than for the more popular keywords where you might be lost lower down in the directory. Knowledge is limited.
Imagination encircles the world.