A loud and strong kiai is important not just for intimidation, but for raising one's morale!
Hit with your body, not your hands. Use your footwork to reach your target.
Beware of your ma-ai. A ma-ai that's too close or too far will result in a hit that's too deep or too light respectively.
Find your bad habits and weaknesses during keiko. Being aware is the first step towards change!
Avoid tensing your arms and shoulders. Grip with correct tenouchi and focus on snapping your wrists for sped and power.