Because these ingredients are missing a certain protein, called gluten, they are used in a different way to wheat flour.
Often you will find that you need to mix a number together to get the best results. Learning which ones to mix can take time, and can differ depending on what you want to bake, so you might like to start with a commercial mix.
Some manufacturers to look out for in the USA include Authentic Foods and Bob's Red Mill. In the UK, most supermarkets now stock Doves Farm.
There are normally some basic recipes printed on the packs, and to a certain extent you can use your own favorite recipes by substituting the flour in the recipe for the same amount of gluten free mix.