There are several basic forming methods. Here are a few:
Isostatic Pressing is the use of force pressures of equal proportion from all directions. Isopressing is commonly used to form complex ID configurations by compressing powder around a pin.
Extrusion is done in the same manner that most materials are extruded, by forcing material through a die. This is a standard process for tubes, rods and bar stock material.
Injection Molding of ceramics is also similar to the processes used for other materials. Injection molding is used mainly for very intricate or high volume components. The cost for injection mold tooling is expensive but when amortized across high volumes it can mean a lower per part cost.
Mechanical Pressing utilizes steel or carbide tooling that creates a "net or near net" shape. By filling the tool with powder and applying uniaxial pressures to compress the powder.
The above forming methods can also be used to make "blanks" for further processing.
This leads to the next step, Green Machining