I too was first inclined to capitalize each word (it is a title, yes?). But really I think it comes down to the capitalization of the word/phrase in use, is what the ‘definitive’ capitalization should be (I also check out how ‘official’ people like MS would spell ‘shader model’, for example, in addition to checking Wikipedia). So proper nouns caps, almost everything else, no.
Unfortunately I often forget or get mixed up when making pages, but making redirects is very simple, so I will almost always end up doing that. I keep an eye on the [w]Special:WantedPages[/w] to look out for broken links that may just need a redirect, and if I happen across a page that should be de-capitalized (or capitalized for that matter) I normally end up moving it.