In reply to cheale:
I had a terrible year last year, but things seem to be better for me this year.
I use nematodes starting in around April and applying every 6 weeks or so. These do not kill adult slugs, but they do kill larvae. For this reason, they aren't a magic solution, but repeated applications will keep the slug population down.
In addition to this, I don't direct-sow anything any more. I sow mostly in modules or small pots. I use copper tape around the rim of these. I have found that this needs to be at least a couple of cm wide to be effective, so I usually do a double-ring of tape. I also put something gritty on the surface once the seeds have germinated. Again, this is not a magic solution, but my survival rate has been much better this year - I've lost maybe a quarter of my seedlings rather than the three quarters I lost last year.
The final part of the equation is to let your seedlings get really big before transplanting them. That way, it's more difficult for slugs to do enough damage to kill them. When I do transplant them, I again surround them with something to discourage slugs. For mature transplant-sized plants, I like sheeps wool pellets for this. You put a heap around the plant and water them - they swell up to form a solid mat. The mat tends to overwhelm young seedlings, but protects older plants quite nicely.