Search Engines Plug in?

Well, I'm going to resurrect an old thread, since this seems the best place to post my question.

How do I create a command string for a custom search engine, so that my search results will display automatically, instead of just displaying the search engine's home page. Looking at all the predefined search engine strings in the plugin doesn't tell me anything, since there's no common denominator from site to site.

For example: I want to create a custom search engine for Wikipedia....
I give it a name, create an alias, and enter

Code:

http://en.wikipedia.org/wiki/Main_Page

in the URL box. But this obviously doesn't give me my search results that I've entered in the command line box...all it will do is display Wikipedia's homepage.

Can somebody please explain how I create the suffix needed to add to the URL, so that the search results display automatically?

Thanks