How to prevent Weeds in Flower Beds

Breaking up the roots of perennial weeds like couch, ground elder and bindweed leaves behind small pieces that can quickly grow into a new plant.

How do I keep weeds from growing in my flower beds?

What kills weeds around flowers?

What product kills weeds but not plants?

Is there a spray that kills weeds but not flowers?

How do I get rid of grass in my flower beds without killing flowers?

Can I use Roundup in my flower bed?