Different species of frogs and toads have different habitat needs. The following is a basic guide, tried and true for our Cuban Tree Frog and Firebellied Toads. Your veterinarian or other experts may have additional advice for your particular companion amphibian.
You will need: two enclosures, two water containers that fit inside the enclosures, and climbing toys such as rocks, branches, or platic branches or islands, water, bleach, and bottled spring water. You can use filtered tap water, but spring water is convenient and we found it worked much better, especially for the Firebellied Toad.
Clean everything with a very mild bleach solution (we used about a capful for a five-gallon tank). Just dump all the toys into the aquarium/container and fill it with water. Add bleach and let it sit, uncovered, for fifteen minutes. Then rinse everything at least three times, maybe more, until there is absolutely no smell of bleach. Ideally, you will leave the container open for another twenty-four hours to be sure every trace of bleach is gone, as bleach will kill your pet.
On the other hand, bacteria and mold in the living area will also make your pet sick. Rinsing is the key to a healthy amphibian. A bonus is that this concentration of bleach won't hurt ornamental plants and the traces of dead skin and excrement from your pet are actually good for your plants. The spot where we cleaned the cages always had beautiful, healthy, grass.
Once everything is clean, set up the habitat. The large enclosure should have solid walls to hold in heat and moisture. An aquarium will do, although for smaller species you can also use a plastic container with many holes in the lid. These are more escape-resistant than aquaariums, not slippery when wet, and are lighter and easier to handle. Just please make sure the ventilation is adequate. You can do this by driving holes in the lid with an awl, hammer and large nail, or heated screwdriver.
You will probably also want a lamp for heat and light. Position the lamp so that the enclosure has a warm side and a cool side so your pet can regulate his or her own body temperature. Temperature and humidity gauges can be useful, showing you if you need the heat lamp closer of farther from the cage, and when to open the lid and let out some moisture. In platic cages, too much humidity can be a problem even for water-loving amphibians.
To reduce the humidity, simply open the cage and let it air out. Also check the temperature. If it is on the warm side, keeping it a bit cooler will reduce evaporation from the pond just a bit. Always supervise your pet when the cage is open. These little guys are escape artists.
Inside the living space, you need a 'pond' large enough for your pet to soak, and if at all possible, swim. You need a dry space for resting and feeding. Your pet needs a way to get from the water to the land or the other way around, so use the branches and plastic toys to create secure ramps. Watch your pet to be sure that the amphibian agrees with your ideas of a secure path and can comfortably access either dry areas or water. Tree frogs will appreciate something they can climb.
Fill the 'pond' with well-filtered and aired tap water or - better - bottled spring or drinking water. Never use distilled water. An amphibian's skin is permeable, and essential salts will leach from the animal into completely pure water. Towards the end of his life, our Firebelly did noticeably better with Zephyrhills spring water than with other brands. Water is an important enough part of your pet's environment that it's worth trying different brands to see if it makes a difference.
Every other day, repeat the process of washing and arranging the cage. This is where it can be useful to have two cages and sets of furniture. One can be airing while the other one is in use. Change the 'pond' water whever it becomes soiled.
As I said, this is the basic set of instructions, and your pet may have more specific needs. Just remember to rinse like a crazy person, air everything, clean frequently, and do not ever use unfiltered tap water or distilled water. Also remember to give your pet a choice of water/land and if possible a range of temperatures within the habitat.