Six essential tips:

1. Starting an article
2. How to add an article to a category
3. Please sign your name on talk pages
4. Edit summary reminder setting
5. Moving pages
6. Redirects

Half-a-dozen power tips:

1. Create links faster with link tricks
2. Power-editing with AutoWikiBrowser
3. Navigate faster using Wikipedia shortcuts
4. Wikipedia industrial-powered search
5. Work faster using keyboard shortcuts
6. Install your first javascript (Watchlist Sorter).

If you know even better tips than these, drop on by the Tip of the day project and show off a little. Strut your wikistuff!