Here you can digest how to use Wikipedia in bite-sized morsels. The tips listed below were created for the Tip of the day project, or the Styletips project, but are listed here by title and organized by subject area for your convenience.
Navigation popups is a script, written in JavaScript (source), that offers easy access to article previews and several Wikipedia functions in popup windows which appear when you hover the cursor over links.
Quick installation: Enter Special:Preferences and click "Gadgets", check the box to enable Navigation Popups, under the "Browsing" section, then click save. Follow the instructions on the page to bypass your browser's cache.