The Main Page is the entryway for most casual readers into Wikitravel. It should show us in our best light, and we've put a lot of thought and work into designing it, to include a mix of gradually-changing information. Any logged-in user can edit it, but because of the complexity of the page layout, care should be taken in doing so.
Destination of the Month and Off the Beaten Path are two featured articles, which are changed every month (on the 1st and 15th, respectively). These articles are selected in advance at Wikitravel:Destination of the Month candidates. If you wish to edit the text or replace the image you can do so, but take care not to upset the page layout.
Discover spotlights interesting and often quirky factoids about the places described in Wikitravel guides. These items are also selected in advance, and added to a queue of upcoming items at Wikitravel:Discover. This section is not updated on the Main Page itself, but in a template that is automatically included in the Main Page.
Travel News features the three most recent travel-related news items contributed by Wikitravelers. These items are generally not selected in advance (for obvious reasons), but can be added at Travel news. Updating this section on the Main Page is tricky, and should be attempted only after reading Wikitravel:How to add travel news.
Collaboration of the Month is single destination article selected for a focused effort to improve it in some way. Articles are selected in advance at Wikitravel:Collaboration of the week, and this item is changed weekly, of course.
Newest "Star" Articles is a list of the 8 most recent articles to be declared "Star" quality. Star articles are nominated and evaluated at Wikitravel:Star nominations, and this section is changed whenever an article passes this process.
The rest of the Main Page should not be changed without first discussing it with the community. The mission statement is dear to many people's hearts, the index of continents isn't likely to change any time soon, and the addition and classification of other-language guides is managed by User:Evan.