What causes snails in gardens? And how can I get rid of them?

Anything u sprinkle crushed egg shells around will act like razors to a snail.

Set out saucers partially filled with cheap beer and salt and the snails will drown in it. You don't want to be putting salt directly on to/into the ground.

Apply food grade diatomaceous earth

Beer on a shallow saucer is said to work, as far as a cause, it's nature!

When I lived in southern CA I had a terrible time with slugs. I used to put a shallow pan of beer out. For some reason they seem to be attracted to the beer, climb into the pan and drown. I'm not sure this got rid of every one, but it did keep them under control better.

Small jar lids with beer.

Although I can't answer how they got there, to get rid of them sink a shallow dish into the ground where they are the most prevalent and fill with beer. They drink and drown.

I did try beer. Left it out for 2 wks.