Wash the container thoroughly with a weak vinegar/water solution. Do not use any harsh detergents as this may prove harmful to the creature(s) you will introduce into this container. Make sure the cover fits snugly, yet allows for the circulation of air. A screen cover is perfect for this. There are various options available for heat and light. You could use a light source that also doubles as a source of heat by virtue of it’s incandescence or, if your container is a fish tank, you can opt to purchase a light fixture at your local petshop that was manufactured specifically to fit that size and shape container. You can, of course, place your vivarium near a window and let the sun do the lighting and heating for you. This is perfectly acceptable provided you keep a close eye on the container’s temperature (hence the need for a thermometer). Yet another choice would be the addition of a "Hot" rock. This is an artificial, yet realistic looking, stone (also available at your local petshop) that has a heating element inside. Once plugged in, whatever animal you have in your vivarium setup will invariably position itself as close to or as far from the "rock" as comfort dictates. A small, shallow bowl can hold water that your vivarium’s tenant may drink from. This is not always true however since some animals prefer to lap up droplets of water from leaves or the sides of the container, such as after a misting, and some will actually absorb needed moisture through their skin. The gravel and soil will form the substrate or ground of your vivarium and will be where you will deposit your plants. One option, which I prefer because it’s so much easier to maintain, is to line the bottom of your container with an artificial turf which can then be easily and periodically removed, cleeaned, or replaced. The plants you intend to use can instead be planted in the flowerpots and placed in whatever arrangement you prefer, this also aids in your vivarium housekeeping. I personally have found that an old tablespoon comes in handy when planting or repotting plants, and the fishnet and tongs allow you to reach into the vivarium with a minimum if disturbance.