During the apocalypse, Glenn goes back and forth to Atlanta to gather supplies. He knows his way around town extremely well because he used to be a pizza delivery boy. On one of his trips, he sees Rick being attacked by walkers, and saves him.

The Walking Dead Quotes

Daryl: You've got some balls for a Chinaman.
Glenn: I'm Korean.
Daryl: Whatever.

You walk outside, you risk your life. You take a drink of water, you risk your life. Nowadays you breath and you risk your life. You don’t have a choice. The only thing you can choose is what you’re risking it for.

Hershel