This year the slugs are absolutely destroying my lettuce and cabbage, I find them mostly in the evening when I go out to check on things. I've tried beer in shallow dishes but it doesn't work that well, and I'd rather avoid using metaldehyde since I've read it's toxic to other animals too.
Slugs hate copper and bran, so you can try putting copper strips around your vegetables or spreading wet bran (slugs get stuck to it). Another super effective solution is hand-picking them in the evening when they're active - yeah, it's tedious, but it really works well if you catch them while they're eating. You can also create physical barriers with rough sand or crushed eggshells around your plants, because these animals can't get through them. If you have the chance, attract ducks or hedgehogs to your garden - they massacre slugs and don't damage the plants.
I think beer isn't as bad a solution as it seems - the problem is that a lot of slugs won't fall for it twice if the saucer is always in the same place. But what nobody ever mentions is the timing: if you go out in the evening with a flashlight and a bowl of salt water, you hand-pick them and drown them directly. Sounds tedious, right? But I have a friend who did it for a whole week at the start of summer and after that the slugs figured out the garden wasn't worth it and looked for somewhere else. Seriously, I'm not exaggerating.
As for the rest, copper really works - a strip of copper tape around the pots is annoying for them on a tactile level. What I'd add though is that slugs go crazy for damp spots and hiding places: I remove all the cardboard, wooden boards and debris you've got lying around the garden, because that's where they hide during the day. If you take away those shelters, they stay more exposed when they have to cross open areas to get to your plants. Combine the evening hand-picking with the lack of hiding spots and after a couple of weeks you'll see the difference.
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