First, the bad news: There are 8 million people in New York City and exactly one full-size IMAX theater, so it's going to be a little while before I get to see The Dark Knight Rises. And since mildly spoilery tweets have already started trickling into my feed, I've set up a full-spectrum ban: nothing with the word "batman" or "dark knight" is going to make it onto my Twitter feed. Here's how to do it.
If you're checking Twitter on your browser, the best blocker is a Chrome plug-in called Open Tweet Filter, screencapped above. It adds an extra "Filter" button to the top menu bar, then lets you block any keyword, hashtag or user you want.
Outside of the browser, nearly every desktop Twitter client has a "mute" or "block" functionality in its settings tab. (Tweetdeck calls it a "global filter," which is what I'm using.) The same goes for phone-Twitter, as long as you're not using an official Twitter app. I won't bore you with a full list, although we're partial to Tweetbot for iOS and Plume for Android. Carbon should be cool too, once it's out.
That said, these are all pretty clumsy tools. Any plausible filter I put up is going to block out a lot of jokes and random non-spoilery observations along the way. Make no mistake: This filter is going to seriously impoverish my Twitter experience for as long as I keep it up — but since this movie absolutely must not be ruined, I'm willing to go nuclear.