Did I mention "Home Depot"? It must be a swear word here. I take it back.
The links that Margaret provided earlier in this thread are very helpful. A few more follow-up questions, if you don’t mind:
On garden beds: Assuming that I’m not digging out the entire garden and starting from scratch again, do I still lay down cardboards for each individual plants. If so, how deep into the soil do they need to go?
On mulch: Some of my garden beds already have a layer of mulch (bark) on top. Do they need to be replaced periodically?
On digging: When I add plants, soil and compost to my garden, what do I do with the old soil/mulch that I dig out?