How to control weeds with newspaper?

So I've heard that laying wet newspaper down around the plants in an existing bed (and then covering with mulch) is a good way to control the weeds from growing in the bed.
First, is this true?
Second, do I have to pull all the weeds first so that I'm starting with a 'clean' surface, or can i lay the newspaper over the top of existing weeds/grass?
Thanks!

i use this method but have never wet it. i always try to weed as much as i can but have been known alot of times just to lay it on the grass and let the grass die off.

i use 2 layers or more. one layer just doesnt do it. then i put mulch on it but remeber to leave the mulch about 3 or 4 fingers width away from plant on all sides as they need to breathe.

if you layer the mulch thick enough and get the weeds before you wont get any. i use pine straw and layer it thick and hardly ever get weeds. i have had beds like this for years and wont do anything else but newspapers and mulch. even our mulch comapnies here tell you to use newspaper or plastic first. i prefer newspaper as it degrades over time.

Thanks for a great answer!

Try not to use the colored paper.Just black and white newsprint.The colored ink is a bit messy when it breaks down.Edge

Works wonderful!!! I do it with all my new beds. I use about 4-6 pages a layer and overlap them so nothing grows thru it. I do wet it.
Do not use glossy paper.

Thanks all! I will try it this weekend.

I wet it to weigh it down until I can get the mulch on it. Keeps it from blowing away while I'm working. I just squirt it with the hose. If I need to fertilize (like using Osmocote), I put that down before the paper.

fertilizing is easier also if you do like i said above leave 3 to 4 finger widths away from plant. great for liquid or the slow reales as it gets to the dirt and dont have to worry about the mulch.

Did lay newspaper down when putting in stepping stones and it worked great to kill the grass...
Also I just found out that if you line the inside of your hanging plants or pots you don't have to water so often! Tried it and it works great! I leave the cocoa liner on outside of pot, then 3-5 pages of black and white newspaper, soil and plants.... also put plants on outside of planter by putting holes on outside of planter in a zig zag pattern, my begonia pot is a solid planter with begonias inside and outside, cannot see pot!

Please stop by and weigh in

-http://davesgarden.com/community/forums/t/1101381/-

The newspaper trick is great for attracting earthworms, keeping roots cool, providing a biodegradable sort of nutrition as it breaks down, and suppressing weed sprouts. HOWEVER if you have bermuda grass in your yard you will continue to fight it because it will poke right through the newspaper and keep going. If you have bermuda, you will have to eradicate every shred of it before you lay down the newspaper. Otherwise you will be wasting your time. (this said by someone who learned that lesson the hard way!)