Follow the trails to see where there are coming in from a put a dose of salt down across it and this tends to stop them as they have an aversion to salt on the basis that it makes them melt and turn inside out.
That is unless you are my dear old mum, who used to have quite a bad slug problem so went out and bought a "bug eyed snail gnome" type of thing and put it in her living room and has never had a single slug trail in her house since. I swear blind that it has to be coincidence, but she says that she read in a magazine somewhere that they won't enter an area where they can see a predator hence her funny snail.
I saw one in my front garden about three weeks ago and it is the first one that I have seen this year. We have a family of foxes at the top of the road and although quite well fed by a few of the neighbours, I have always put the lack of hedgehogs down to them keeping the population in check, as we have a lot of slugs and snails here.