I bought a roll of copper mesh from Lee valley, I've had it around the base of a Ligularia for the last 4 years and it has helped a lot, there are one or two holes in the leaves but at least it doesn't look like swiss cheese.
I'm trying the coffee ground thing around my Hostas, from what I've read slugs don't like caffine.
A......

I just talked to somebody who said that copper did help a lot. I have used foil but I think it was not sturdy enough (bought it at Smith & Hawkins) and it did not make an ounce of a difference. After talking to this gardener I am hoping that if I ever try this again, the success rate will be worth the money.

Copper is helping for sure. I got some old copper pipes from plumber, flatten them with hammer and made barrier around each bean plant. they are happy and i too.
DE is helping as well, but coffee grounds are not working for me. I brought from Starbucks plenty of grounds and put around cabbages. Looks like slugs enjoy them.
I have sprayed my lettice with garlic & hot pepper spray to get rid of tiny slugs. Will see if it helps.

I bought copper roll some time ago.Can someone please let me know how do you place it? I put it once around few plants and the little slugs got to my plants despite it? Maybe they were already there? I would imagine it would go easily around a pot, but if I have lettuce scattered all around other plants so the slugs wont find it how do you apply it ? to individual plants all around the garden? or what? I can cut to size but I am not using it as yet? Any suggestions please and thanks..

Okay, this may not be as popular an answer, (and the doing it once and leaving sounds better), but you might want to consider Escar-go from Gardens Alive for your really tough slug problem. I had a TERRIBLE time when I first moved here, and this is a product I can easily endorse. Read about it on their website, but I think most organic gardeners would be comfortable using it. Very safe around pets and kids, easy to apply. Be interested what you think of it.

I'm glad you mentioned pennies because I tried it. I filled a plant saucer with pennies and dropped a slug in it. It just wandered around in there for awhile, then left. No sizzle, nuthin'! Anyway, I gave up on that idea but it seems like it should work as well as a copper strip.

The copper won't kill the slugs. The mild electric shock they get is meant to be a deterrent. Your slug would of course hightail it off the copper as fast as a slug can go! LOL!

The idea is that a slug would not choose to CROSS a copper barrier.

I bought the copper mesh from Lee Valley (it comes like a rolled up sock) and cut into two pieces so it would cover more. Either it doesn't work very well or I must have some of the toughest slugs around because today there is one just happily sitting on the mesh and is far from "hightailing it". Maybe by cutting it I reduced the effectiveness? So I might try the copper tape next and, failing that, go barbaric and use slug bait. They've already destroyed my marigolds and are now after my gerber daisies. When's summer? ;)

3 yrs ago i made 100s of hosta rings from rolled coils of aluminum? sheeting. I cut strips of copper foil and crimped it around the upper half of each ring. i placed these around my hostas, copper up to deter the slugs crawling over.
what a waste of a few evenings. Ken A on the hostas forum has said this copper barrier 'solution' doesn't help because the eggs are already in the crowns.also, the slugs can travel from leaf to leaf without hitting the ground. so i've started doing the 10% ammonia, 90%water drench inside the crowns and outside the crowns. so far so good but we shall see. i know he repeats his treatment.
i don't know if 10% ammonia would hurt you for edible plants.
best,
mindy

NOT tarnished copper...
I was intrigued about slugs and copper, so conducted my own little experiment. I put 1/2" copper pipe in the sun, and a slug so that, with the sun at his back, in his retreat he would be forced to come face-to-face with the copper. He touched it and reared back like a miniature horse! It worked, and I read later that their reaction is caused by a small electrical charge.
----
One drawback about copper I've never seen addressed in forums or blogs, on garden sites, or by garden suppliers: once the copper is tarnished, slugs cross it like it's nothing.
I don't feel like cleaning my copper, nor wish to rebuy every season, so I've opted for ducks. They're fun companions (in the country), but the hens can be loud. Better to have a drake in town, if slugs are a problem there.
God bless your Garden

--CharlysGardenPlace

I had two rings of copper and the slugs just marched right across them (I watched), so I'm not a fan of copper, but I did want to reply to the "how" question. I opened up some paper clips part way and just staked the sheets down onto the soil.

I also have tried rings of ash, coffee grounds, and egg shells, to no avail (a moat of water or ring of salt does work for containers though). For some reason, this is the first year I haven't had many slugs, so I actually have greens finally.

sluggo is decently effective for me. seems cheaper and easier than copper.

Copper ? not a practical way to combat slugs.MO. If you have just a few plants, you might try it but for a garden over 100 sqr-ft , it is not practical.

Number one, and best combat is to hunt them, at night , in the mornings, ... and destroy them. At the same time use slugo type stuff. I use BUG GRTA.

I am also experimenting with some home recepie. Coffee grounds from your coffee machine (or starbucks..) seems to be effective too. I add some fine sand to it and I also grind egg shells in coffee mill and mix with it. SAND & EGGSHELL have roughness that slugs will get wounded when crawling on them, unlike the chemicals that do it chemically wounding their belly.
Yesterday, with overcast skies and some rain, was a perfect day to hunt slugs. They come out during days like that and it is much easy to spot them. I DID that and, even though there are not that many of them in all of my veggies and flower gardens(after combating them last year and this year) yet I found some of them, mostly in non-critical areas. I did that because I do not want them exist, spread, lay eggs, etc. I found them mostly under the dead daffodils tops, in the cracks.. So it can also help if you know where they hide . then you get them.

To summarize, fighting slugs in a wet , damp, rainy climate is an ongoing battle. But once you minimize their numbers, it get easier. The serious danger is to the small seedlings, early in the season.

I find putting tempting daytime hiding places about the place and then ambushing them whole they sleep good. I'm also starting to see that you have to go at them on several fronts combined.

I like sluggo for perennial beds, but the squirrels and now the Steller's Jays eat it like candy. So I can attest to the safety to wildlife, as neither numbers have been diminished.

The best other method I ever found was using small waxed containers, like pint or 1/2 pint milk, cream, or half and half containers (maybe can get some from a school lunchroom). I squirt deadline in them, since I don't want it in the dirt, lay them on the ground with the spout open. The slugs love that stuff. They crawl in to eat it and never crawl out. I then just pick it up and toss it, never have to deal with the corpses, replace with fresh ones. They are easy to tuck under plants and hide pretty well.

Beer baits have worked best for me. I keep little plastic containers from the recycling (from apple sauce) Pour a little beer (or you can use brewers yeast) in the cup - push into the soil so the top is level with top of soil. You can pick the slugs out the next day and just keep topping up the cups when you need. This is the one tried and true after trying MANY OTHERS. Hope it helps.

With the beer traps, can one put lids on and cut entrances towards the top - or would that render it ineffective? I'm thinking about evaporation. I'm hoping the tiny ones love beer as much as I know the big ones do.