Direction of force is given by Fleming 's Left Hand Rule.See image here. Arrange your thumb, index finger and middle finger in such a way that thumb points up, index finger points front and middle finger towards left. Then thumb denotes direction of force, index finger direction of external magnetic field and middle finger direction of current. I couldnt post an illustration for this, as I am using my phone. Maximum force is experienced when current flow in conductor is perpendicular to magnetic field. Minimum force when current flow in conductor is parallel to field.