Firstly, please make sure you aim Sphero first.
Sphero has a unique turning circle. When first driving Sphero we recommend driving in an open area on the "Cautious" speed setting. Doing this will allow you to understand how Sphero maneuvers and enable you to control him more effectively at his "Crazy" speed setting.
Sphero is like a sophisticated Segway inside a ball. Therefore he does not turn on a dime but more in an arc like doing a U-turn in a car.
Smooth movements of the joystick in different directions allow more the most successful control of Sphero. Try it out!