How do you get those white O rings out?

[Nick Seymour]

This may seem like a silly question. I don't want to damage the rings. I feel that a flathead screw driver would be the easiest but using that may do damage. 

[Rob Courtney]

Toothpick?

[xpsTech]

Don’t worry about the big o-ring embedded in the underside of the cap, that is an air side seal so it doesn’t need to be removed for cleaning (not in the beer path). Same for the small o-ring under the air valve. 
 

The one that does need to be removed and cleaned is the small o-ring under the beer valve. 
 

As Rob said, a toothpick or something that is smooth without sharp edges to avoid damage. I’ve fashioned a thin “shim” from a plastic milk bottle  that I slide between the o-ring and the thread to gently pry it out.