Backing up the database is great - but I've yet to see a clear and concise set of instructions for doing so which doesn't assume a lot of knowledge and experience on the part of the user. For example, I exported all my pages once - and there were maybe 20 or so - and could not re-import. The default settings for memory wouldn't permit it and I never was able to figure out exactly what to tweak to get this basic functionality working.
http://www.mediawiki.org/wiki/Manual:Backing_up_a_wiki
That documentation assumes a lot of knowledge? If you let me know what isn't clear enough, I'll take the time to modify it.
V/r,
Ryan Lane