Using Vermicompost (worm castings)
For plants in pots and containers, I suggest mixing 25% worm castings into your potting mix. This is about ideal, but experiment. It may vary according to what you are mixing with. Worm castings are great for starting seeds. Just a little tid bit: Worm castings contain 5 times more nitrogen, 7 times more phosphorus, and 11 times more potassium than ordinary soil.
Worm castings can also be used as a compost tea. Mix two tablespoons of castings with a liter of water and let it stand for a day, shaking occasionally, then water under the plants. (One liter water bottles make a good watering container if you drill a few small-diameter holes in the lid.) Compost tea is great to use when transplanting. Using a slightly diluted version of your compost tea will help prevent transplant shock if you water in your plants with it afterwards.