It is important that you prepare a good home for your savannah monitor. Issues addressed include: the enclosure, heating, substrate, water, and shelter.
The Enclosure
Savannah Monitors should have an enclosure that has height and width roughly as long as the lizard (from the tip of its snouts to the end of its tail) and length twice as long as the lizard (from the tip of its snouts to the end of its tail). Building or buying a cage are both options, but either way, make sure there is no way for your lizard to escape. Using wood and strong mesh, such as chicken wire or rabbit fencing, work well for Savannah Monitor cages. If you are building an outdoor cage you may want to build Plexiglas sides to provide insulation from the cold. Try and keep decorating to a minimum because Savannah Monitors will destroy whatever they can. Make sure that the Savannah Monitors enclosure will be easy to clean.
Heating
Savannah Monitors come from hot, dry environments in the savannas of central and sub-Sahara Africa, but make sure the monitor's enclosure doesn't get too hot in the heat of the day. There should be a part of the Savannah Monitor's cage permitting the animal to cool off if necessary. Providing shade, shelter, and water are a good idea.
Light Source - There should be a basking spot in the cage provided by artificial or natural ultra violet light, possibly by means of a basking light, which should remain on for most of the day depending on how hot the weather is outside. It is best to have the Savannah Monitor exposed to light as close to natural sunlight a possible. Savannah Monitors like to be exposed to 12 hours of light a day.
Heating Element - A Savannah Monitor should also be provided with a heat element such a ceramic heat emitter, light, hot rock, heating strip, pig blankets, etc. This way your lizard can keep warm, but make sure you do not have too much heat because monitor lizards can burn badly. They will ignorantly expose themselves to heat which can result in serious burns.
Substrate
Make sure to use a removable substrate in your Monitors cage, because it may need to be replaced frequently. Artificial turf, butcher paper, or newspaper work well. These are some of the best substrates because they can be removed if defecated on. Artificial turf can add a nice touch in a Savannah Monitor cage, but it is not that easy to clean. Other substrates include gravel, dirt, and wood chips.
Water
A water dish, preferably one in which a Savannah Monitor could bathe, should be provided. Savanna Monitors frequently defecate in water. Place the dish in a spot where it will be easy to check and clean regularly. Savannah Monitors will drink water when they are thirsty, and you probably don't want your monitor drinking in the water it defecated in. Savannah Monitors are also fully capable of swimming and they can even swim under water
Shelter
Savannah Monitors are shy creatures, so you will have to provide them with some kind of shelter. The simplest and most cost effective hiding place that you can provide is a cardboard box. As your lizard grows it will need a bigger hiding place, so you can simply find a bigger box. Some other options include building or buying a shelter, but commercial shelters can be expensive and hard to find for larger lizards. Keep in mind that cleaning is still an issue with shelters because they are not impermeable to lizard feces.