Where can I buy stone? What are the different kinds of stone that are available? What do I look for?
Stone is available from building and construction stores, stone suppliers, direct from the quarry and, occasionally from construction sites when you have permission.
Although most of the planet is made of stone there is only a small fraction that is useful as building material for steps and walls and patios. Stone that is all about the same thickness is the most important factor when building steps and patios.
Where I live these types are commonly available:
Building and construction stores sell stone by the pound. This price is usually at a substantial premium to buying by the skid but handy if you just need one more piece.
Stone suppliers will source material from around the world are a better decision if you want a wider choice. They will usually deliver and often supply the gravel and stone dust that you will also need. Stone is usually sold by the ton with a pallet holding two tons. Assume one person and a wheelbarrow can move one ton of stone an hour over a distance of a hundred feet.
Quarries sometimes sell directly to the public and this is the best price you will get as there are no middlemen. They might or might not deliver and usually only stock what they quarry.
Construction sites are another source of stone if you are reasonable. First thing to do is ask if you can take some stone! Some sites are removing stone and are only too happy to have you do the job for them. Other sites are filling and view the removal of raw material as stealing. If the stone has been blasted out it is not as suitable for building as the blasting process causes micro fractures. Later your "free" stone can start falling apart causing you to need to rebuild your project. This stone can be used for walls but is rarely suitable for steps or patios.