You can purchase polymer clay in hobby and art shops. Polymer clay is easy to work with and can be dried in your oven at around 275 degrees F in minutes, depending upon the size of your sculpture. This makes polymer ideal for beginners. You can paint and glaze polymer or even sand it to a shiny finish, so you might want to consider having sandpaper, clear gloss and acrylic paint on hand.
Tools for sculpting clay are quite simple. Clay scrapers, wire tools and spoons are all available in wood or metal at hobby and craft stores. You could even use a kitchen knife, spoon and toothpicks if you don't want to purchase tools. Polymer is versatile and easy to work with. A lot of the work will be done with your bare hands.
Mix the clay you'll need for the size sculpture you'll be working on. You want to find a place to work where you can set up and leave your sculpture and tools unattended without fear that anything will happen to them. Start your clay sculpture on a board or some other base to make it easier to transport.
Be prepared to get your hands dirty. You'll start your sculpture by manipulating the clay into a rough shape of the sculpture you want to achieve. Get the shape as near as you can. You won't be thinking about details at this point. They come after you have a base shape to work with.
Use wire clay cutters and clay detailing tools to work the details into your sculpture. If you're doing a human bust, you can use a clay scoop and clay palette knife to add facial expression and depth. The good thing about clay is how easy it is to correct any errors, so don't be afraid to get experimental. Keep a little rubbing alcohol or even water nearby to smooth your clay as you sculpt your details. Keep a mirror handy. Looking at your sculpture in a mirror makes it easier to see when your sculpture is crooked.
Many sculptors prefer the look of untouched clay. You can sand your polymer sculpture to bring out a sheen in the clay. You can even add clear gloss or paint your sculpture with acrylics after it's been hardened in the oven. Polymer dries quickly in the oven, so it's best to keep an eye on it during the drying process.