Use the edge of the racquet to lead the service motion into the ball.
Most players turn the strings into the ball too soon and lose power.
It is much more efficient to keep the edge as long as possible, and instead of turning it consciously, which usually results in a weaker serve, keep the edge until panicking, feeling like you are going to cut the ball in half.
Your instinct will turn it at that later stage with a fury, resulting in a much stronger hit.
Give it a try, be brave in keeping the edge towards the ball as long as possible, and you’ll see incredible spin and power results.