See, right now, there's basically four ways.
One way is to merchandize like crazy - go the Sluggy/PA route. It works, if you're superpopular. If you're not, it doesn't.
One way is to sell out. User Friendly is king at this. I will say no more about it.
One way is to put a donation button on your site and pray. Again, if you're superpopular, it works. Otherwise, it doesn't.
And the last way is to lock down your comic and make people pay to look at the archives. "But why do you mind? You could just read it every day!" you say, entirely correct and entirely missing the point. Fans did this. I no longer read Fans. If they hadn't picked a downswing in comics quality to do it during, I might have even subscribed, but they did, and now they've lost my readership forever. (On the plus side, cognitive dissonance kicks in and you're basically ensured that everyone who pays money to you will claim your comic rocks.)
So here's a new method I just came up with.
You write comics three months in advance. And you post them for the people who subscribed.
Want another three months of comics? Subscribe and you'll get 'em! Don't want to subscribe anymore? Not a problem - you'll just have to wait three months to start seeing new comics again.
Of course this won't work with everyone (I'm chucking at the idea of PA trying to implement this - worst idea *ever*) and, as usual, TANSTAAFL (There Ain't No Such Thing As A Free Lunch - in this case, you'd split your fanbase among subscribers and non-subscribers). (And again, you've got cognitive dissonance working for you, but in this case it can backfire in three months when the mass of nonpayers suddenly say "hey, this comic sucks!".)
And you'd want to be very very careful with it - don't say "well, the rest of you aren't getting comics for three months". You'd have to just work up a three-month buffer without telling anyone until you were ready. And, even worse, you would *have to stick with it* - no unplanned hiatuses - and that alone would eliminate, what, 80% of the webcomics on the planet? 90%?
But I think it's an interesting idea. Anyone see any serious flaws with it?