Unfortunately, there's no great secret to obtaining an effective search on the KoL Wiki just yet. Your best bet is to use the simplest keywords as you possibly can. For example, if you want to find the recipe for bat wing chow mein, try searching for bat wing chow mein. If you want to know all about orange traffic cones, try searching for orange traffic cone.
Just remember to K(eep) I(t) S(imple) S(...illy). KISS.
Quick and easy searching with Firefox
Install a search plugin for the wiki by going to TheKoLWiki Firefox plugin and clicking on the link that says "TheKoLWiki." This will add a search engine with the same name to your search box. Type into the search box, or drag selected text from any page in KoL into the box, to make it work.
Context Search & Search Engine Ordering
Once you have the search plugin installed, you can use the Context Search Firefox extension to make searching even easier. Installing this extension changes the usual "Search Web for" context menu item into a menu containing all of your search plugins, as the image below shows.
In addition, the Web Search Pro Firefox extension is a useful tool for arranging your search plugins in any order you like. Since this feature is available by default in the current version of Firefox, this aspect of the extension is only helpful to people with older versions of the browser.
Another way to make searching easier is to use the following script to insert a link to the corresponding KoL Wiki page after any item's name.
In order to use this script, just go to Bookmarks (Ctrl+Shift+B) and right-click in the list on the left (or right-click on your bookmarks toolbar, if you have one), click "New Bookmark," and paste this script into the "Location" box. Then, when you need a link, just drop down your Bookmarks menu and click the script. It's that easy.
The Greasemonkey Firefox extension allows user-made scripts to be run on virtually any Internet page, making it possible for modifications to be made to those pages. This tool has allowed many of KoL's players to create tons of useful scripts. Numfar has created a Greasemonkey script called WikiLink that adds a small link to the KoL Wiki, similar to the bookmarklet above, next to every item, effect, monster, etc., in the game. You can read more about this script here. After you finish reading, check out the list of Greasemonkey scripts, and see if any others can help you out.