How can I kill weeds and grass from growing in my flower beds?

Putting any type of herbicide in a garden is not a good idea.Firstly weed garden by hand, then before placing plants lay a sheet of garden cloth ,its black.lay this sheet over dirt ,make holes ,small one as you plant,this will prevent any other growth and will diminish water needed.If garden is one you cant remove plants ,well it makes placement of material more difficult, you can use newspapers for a similar effect,In my flower gardens I weed then lay down a colored Cedar mulch, red/black/natrural- cover ground around plants about 1.5 - 2 inches thick, very little weeding will be necessary, an occasional weed.c

Once you weed the bed, sprinkle preen weed preventer. It helps alot and doesn't harm the plants.

I use the weed, newspaper or cardboard and then mulch technique. It really helps.

Pull up all the weeds that are currently there by the roots. Put down a thick layer of newspaper, wet it, and put some mulch on top. I tried this and it works well, there were a few little weeds that managed to sneak through and survive, but nothing compared to when I just had mulch down.

A lot of people swear by pouring boiling water on the root system. It's easy and cheap and if it works, you save time and money.

https://www.youtube.com/watch?v=dZX_5xW3ck8