That's a whole lot of info you're asking for, you may want to try starting a thread in the "new to the hobby" forum and then ask questions about clownfish after your tank is cycled and running. But basically the major issues you will face with a 10 gallon nano is salinity, temperature, and water parameters. With such a small volume of water you will have large swings in temperature and salinity throughout the day. You will need and accurate thermometer and hydrometer to keep track of these two parameters. A heater will be necessary to maintain a warm temperature, and possibly even a chiller or a fan if it gets too warm.
Live rock will be a must to act as your biological filtration. All the microorganisms in and on live rock help extract nutrients from the water column and cycle them to gases. There are lots of articles on the Nitrogen cycle, phosphorus cycle, etc available. Live sand is also a plus, but not necessarily a must. I personally use reef rubble instead of a sand bed.
If you want to grow any kind of corals then you will need to have a proper lighting system. For a 10 gallon I would suggest building an LED light system that has high output and low energy consumption and low heat production. A small T5 fixture will also work. Metal halides are great for growing corals, but burn electricity and can easily heat up a 10 gallon tank.
A protein skimmer is also a helpful peice of equipment that helps remove nutrients from the water column and prevents any kind of spike in nitrates/nitrites etc. Some people have been successful without proteinskimmers, but you must have a lot of biological filtration and do regular water changes.
My first step would be to purchase a tank, heater, light, powerhead or pump for water flow, a protein skimmer, salt, pH and other water test kits, thermometer and anything else you need to set the tank up (stand, lid, etc) Next I would fill the tank with salt water and make sure the salinity is correct, then purchase About 10-15 pounds of live rock from a local fish store (and live sand if you want) and let the tank cycle for a couple of months to allow the microorganisms to colonize the tank completely and reach stable populations. Then I would begin to add live stock like hermit crabs and snails. After that I would begin adding fish, two clowns will work just fine in a 10 gallon tank.
I'm sure I've left a few things out, but you're free to personalize your setup however you like. This forum is full of people willing to help. Good luck!
