The comments about improving soil are right. You want to keep it on the dry side. Damp soil just encourages slugs: in the dampest part of my garden I have a plague on the driest part I have none.
Nematodes may work but it is still too cold for them and you need to apply it all the time and they cost loads. Egg shells, coffee and wood ash are urban legends and do nothing to stop slugs. Wood ash is harmful to acidic loving plants! So ignore those as all you will do is waste your time.
Best thing I ever used was slug pellets - kills loads and few of my plants have damage and seedlings actually make it.