The frustrating thing for most people is that our software does not have a "Start new page" command anywhere on the screen. This is actually by design, not a mistake. The theory is that new pages should be linked from older pages, and be part of the cohesive whole of the Wikitravel site, not isolated and on their own.
The best way to start a new page, then, is to create a link to that page from an existing page, and then follow that link to edit the page. We prefer that you start at the Main Page and browse around (use the "more..." links), or use the search functionality, to find a related topic. For example, if you're going to write about a city, you might search for the guide for the country or province where that city is, and make your link there.
If there's really just nothing related to link from, just enter the page name into the search box, you will get an option to create the page.
To create a new link using Wiki markup, type the title of the new page -- preferably conforming to our article naming conventions -- somewhere on the screen, placing it between double brackets, <nowiki>Like this</nowiki>. This will create a link to a new blank page with the title you specified between the brackets.
Remember to start new pages in the correct namespace. Generally this means that pages about using or contributing to Wikitravel -- like help pages, policies and guidelines, article templates, and articles explaining the project -- should go in the '''Wikitravel:''' namespace. You just need to make the link have '''Wikitravel:''' at the beginning, <nowiki>Wikitravel:Like this</nowiki>.
Don't feel like you have to cover your '''entire subject''' in one go. It's OK to just get started with an outline for the article -- you should start with the appropriate '''article template''', and add choice information as you go.
If you make a stub to start the article, other people will follow your lead and add more information. '''Something is better than nothing''', so plunge forward and start that page!
You can easily use the images of wikitravel/shared in the wikitravel guides.