This (rainy) time of the year is when you start seeing some serious slug problems if your garden is "blessed" with this pest. Of course, prevention is the best remedy, but eradication, to some extent, is possible. Some folksy remedies that aren't too effective and some others that are quite effective:
Ducks – These wonderful birds love slugs and snails and eat all they can find. However, they will trash your garden in the process. Not recommended.
Beer – While you may find slugs drowned in your beer bait, this method doesn't significantly reduce their numbers.
Diatomaceous Earth – The sharp edges of this material is supposed to shred the slugs as they crawl over it. That may be true, but this method is not time or cost effective since you must reapply the stuff after every rain or watering.
Boards and pebbles – Our favorite non-chemical method, though it does require time and diligence. Place a board on the ground where you have a slug/snail issue. Place a few small pebbles between that board and another you place on top. Think of a "pebble sandwich" with very few pebbles. Wet the boards down. In the morning, check between the boards for slugs or snails. If they are present, remove the pebbles and press down on the boards to crush the offenders. Reset and repeat as needed.
Deadline – This is the only slug bait that we have found to actually work! (And we have tried many baits.) We swear by the stuff. We recommend 3 applications a year: once in early spring as plants emerge, again mid-summer, and a final time early fall. We have found that a year of using Deadline in this manner greatly reduces future outbreaks. A little goes a long way! Always apply as directed on the package. Properly applied, it poses no threat to pets or birds. Keep small children out of treated area.
Remove leaf litter and dead plant material on a regular basis.
Mulch with a dry surface mulch such as cypress or cedar mulch (not chopped leaves).
Water plants in the morning so ground is dry by evening when the slugs are more active.