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.
Please summarize your work using theEdit summary box
If you make anything other than a minor edit to an article, it helps others if you fill in the edit summary. Edit summaries are visible in the page history, watchlists, and on Recent changes, so they help other users keep track of what is happening to a page.
If you use section editing, the summary box is filled in with the section heading by default (in gray text), which you can follow with more detail. You also can put links to articles in the edit summary. Just put double brackets around [[the article title]] like you would normally. The summary is limited to 255 characters, so many people use common abbreviations, such as sp for correcting spelling mistakes, rm for remove, ce for copy-edit, etc.
Your sandbox is a place for you to experiment with wikicode, to keep notes, to draft sections to add to articles, or for any other purpose that helps build the encyclopedia. Although your sandbox will usually be left alone by other editors, you do not have 100% control. It can't be used to host copyright violations or personal attacks on people, for example.
Have you ever added an example image to a page, only to have it removed and receive a warning? Here's a solution. If you want to test some unfamiliar wiki-markup, or practice image placement, head to the Sandbox, where you can test to your heart's delight (or you can create your own sandbox for more demanding tests). Or open your own sandbox by clicking on "Sandbox" on your user menu at the top of the screen.
Bonus tip: you can have as many sandboxes as you like, but only one gets displayed at the top of the page. To get to the others easily, you could list their links on your sandbox page, using it as a menu of sandboxes.
For a listing of current collaborations, tasks, and news, see the Community portal. For a listing of ongoing discussions and current requests, see the Dashboard.