The garlic mixture can be used as frequently as needed and so far has kept slugs and other creepy crawlies off my Hostas.
1. Chop finely a couple of garlic cloves and put in a roughly pint jar with a screw on lid. Make sure it won't break when you add the boiled water.
2. Add boiled water carefully to the finely chopped garlic cloves, put on lid and soak in the water for two days or longer.
3. Remove the garlic pieces from the water or if too lazy for that carefully pour some of the mixture into a spray bottle or some into your watering can.
4. Spray on plants as often as needed. If you haven't removed the bits be careful not to bung up your spray gun and use the last bit in your watering can without a rose attachment and the bits of garlic can be left to come out around your most damaged or potentially damaged plants.