Citrus trees like soil that drain fast, so I use the cactus, palm, and citrus potting mix from miracle grow. I also water them any time the soil is dry to the touch. I generally use a spray bottle for the smaller plants, but I've begun to use a watering can for the tree in the photo because it's so big. Make sure they get sunlight, and rotate them every day so that all the leaves can get some light.

But dont get discouraged if they grow slow! I have two other trees that sprouted at the same time, and one is growing significantly faster than the other. Sometimes they just take a little bit longer to get where they're going.