Rather than slugs, it is more likely you have porina or grass grubs at this time of the year. They are both very common at the moment. Porina feed on the grass at the top of the soil and leave little pencil shaped holes in your ground. Grass grubs are about ½ a cm long and eat the roots of the grass. Both can be killed using Diazinon. Simply follow the instructions and then apply fertiliser and grass seed in the bare spots of your lawn.