Carefully. All e-ink has a brittle glass substrate layer. My first e-reader, a Cybook, I broke by stumbling, dropping my bag and falling on top of it. Recently, I've got a small crack in the corner of my PB360 - not sure how it happened - I've been careful.
Generally, I try to avoid getting the e-reader in a position (such as in a backpack or purse) where it could twist or bend, e.g. I'd put it in vertically and if possible flat along other stiff, flat objects, like my netbook or books and such. I use covers that are stiff and re-inforced so as not to get pressure on the screen.
I once read here about a user who'd put his e-reader on a foot-stool and accidently broke the screen by putting his feet on it. Since then, I've avoided laying an e-reader on foot-stools and sofa cushions where I could accidently damage it because I was distracted. I do it because I know myself. Even if I don't want to, at some point I'll end up acting clumsily or carelessly, and prevention is better cure in my case
