As a wiki content contributor, it seems like the only easy entry-level approach is to find a category that's interesting to you and largely abandoned. For example, any non-famous books by your favorite author are likely to have stubs or no articles at all.

Of course, if the article doesn't exist at all, you risk a war with the deletionists who've decided certain turf shouldn't exist. And occasionally there's a one-two of one user shredding an article as "excessively detailed", then another nominating it for deletion because it lacks content...

But overall, I've found it a more approachable way to contribute than trying to change or extend any article with an opinionated 'owner'. (At this point, I suspect Wikipedia's factual errors are less likely to come from "anyone can edit" than from possessive and mistaken writers actively restoring errors.)