Flowerbeds? Or vegetable gardening. I would tackle each differently. Here's what I do for my flowerbeds, and trust me, we do have quack grass here!
First and most important, mulch! I use bark mulch. A thick layer of it. I use the biggest size, which makes it easier when you're moving plants around. That small chunk stuff isn't easy to stop falling into the holes you dig when things are being transplanted.
Secondly, a border to stop the bark mulch from being all over the lawn. Lately, I've been picking up peoples' renovation leftovers of their stone brick tiles, real cheap, off Kijiji, etc. I line the flowerbeds with it. Looks great! Underneath the tiles, I use something to block the quack grass from coming up between the tiles, like cardboard cut in lengths to fit underneath.
Thirdly, patrol!!! Every day, take a walk through your flowerbeds, checking for weeds or grass. You're probably out there anyways, deadheading flowers or watering or just enjoying what's there. I know I am. The quack grass will still come up! But...! Using these three steps, I do very little grass pulling now. I do have one area that I have hens & chicks in so I can't use bark mulch in those areas and that's where I do most of the patrolling and pulling of every single little grass leaf that dares to poke their little heads up. But even that amounts to only about five minutes every two days.
Open this up for the wide view:
