Copper slug tape I have used for a while now and it works it gives off a vv mild electric current and they do not like so they do a u turn its cheap on ebay.

The only thing I found with copper is that slugs can extend themselves to 30CM (the big black ones), so all they do is extend onto a low lying leaf and get up to a plant in a pot/tub/basket that way and bypass the copper ring. The copper will stop the small slugs and snails though, but needs to be quite broad - say 5CM min.

Vaseline smeared round the base,and the top,works for me with pots,etc..and do a daily check under the rims..they hide there till evening..!

I have found vaseline works well too and it is cheap. (£1 for a big pot from the pound shop) I have also managed to keep them off my hosta this year too. I am lucky to live near the beach in Dorset so when I am out I collect a feww shells, break them up witha hammer and put them round the base of any vulnerable plants.