I've been having wonderful success in reducing slugs in the spring in my little garden, by collecting them in the autumn. Reducing their numbers in the fall will help reduce numbers in the spring.
In my boyfriend's garden, I strategically placed larger stones/rocks close to plant material that slugs love. Within hours the slugs gather beneath and even stick to the base of the stones. One other trick is to water the rocks in the evening and place some organic matter beneath. Make the stones wet enough to keep the slugs moist.
We placed some more rocks last night and today, within 5 minutes of lifting 4 stones, I found a big handful of slugs.
Great treat for the Koi who devour them feverishly.
If you don't have Koi, just place the slugs on the driveway and wait until the birds come to feed. Or just put them into a hot pail of soapy water and dispose.
Less slugs overwintering, means less eggs and less damage come spring time.