When the propeller is viewed from the airplane cockpit, the prop should be going clock-wise. When viewed from the front of the plane it should be going anti-clockwise.
Glow engines will run in both directions. Make sure your electric starter is turning in the proper direction. (these electric starters will run the wring way if the wires are hooked to the wrong poles of the battery.
If you are hand-flipping the engine to start it, some engines will start backwards. Use an electric starter, or try flipping it backwards.