Design your concrete sculpture. You may work from a reference photograph of something you'd like to create, or you might want to design your own sculpture. Have a solid reference in front of you to work from before you begin.
Select your tools. It's a good idea to have a hammer and several different size chisels available. Many of the same tools you carve stone with will be used in sculpting concrete. Power chisels, engravers and grinders are a good idea if you can afford them.
Build a structure to give your concrete a form you can work with. Use 2x4 wood or plywood to build a solid structure to contain your concrete, then mix the concrete according to the directions on the bag and pour your concrete into the structure. Allow concrete to dry for 24 hours before making an attempt to work with it.
Remove the wood structure and begin working with your concrete sculpture. Decide whether you'll will be cutting a design from the concrete block, such as a bird bath or a personality statue, or if you will be doing bas-relief. Bas-relief is cutting shapes and images in the concrete so it appears as if the images are coming out of a background.
Start with a chisel and carve the basic outline of your sculpture. Work slowly and ensure you don't take too much concrete away at a time. You will do several passes until you have the general shape of your sculpture in place.
Go back over the outline of your sculpture with refining tools. These will consist of several smaller detailing chisels which will allow you to begin adding details to your concrete shape. Work until you have roughed in all the details of the sculpture.
Use power sanding tools and hand files to refine the details of your sculpture and to smooth the sculpture until you have a finished art piece. You can leave your finished sculpture natural or use acrylic paints and gloss to give it a full color finish.