In a rush, or just feel like some instant gratification? Buy a hanging plant, chop off the hangers and put it in your favorite container - pot and all and you have a great looking, instant container garden.
What to do if your container doesn’t have holes:
You can drill them or, if you can’t drill them (or just plain don't feel like it), you’ll want to make sure your plant will sit well above any water that accumulates. To do this put something in the container to lift the plant off the bottom. For large containers, you can take a plastic, one gallon, milk jug, cut it in half, and put it upside-down on the bottom and put your plant right on top of it.
If your container doesn’t have good drainage, make sure to empty the water out of it every once in awhile. If your plant has gotten soaked, let it dry out a bit before you put it back into the container.
What to do if your plant is too small:
If your plant in its pot is too short for the container, you can do the same thing as above – put something in the bottom of your container. It may take a few tries to find the right size to lift your plant up to the rim of the container. You can use a pail or a flowerpot turned upside-down. Plastic food containers also work well.
If your plant in its pot is too small and doesn’t quite fill the container, you can use Spanish moss to hide the edges.
But the easiest way to cheat is to get a big, full plant, like a calibrachoa or fuchsia that will drape over the edges, hiding a multitude of sins.