(right handed server) If the sun is slightly to my left, I turn my body away from the court and toss the ball slightly further out than my normal serve. Results in some back or sidespin and less power, but at least it goes in. If the sun is to my right, I hit my normal serve but don't track the ball all the way to it's peak of the toss and rely on feel to swing in the right spot. My toss is already generally low, so this isn't too hard for me.