Side-arm molotovs, don't throw them over your back like you would a baseball.
Unless you know exactly how to make a watertight molotov, there's the possibility that you drip burning fluid onto yourself if you throw it up and over your body.
By throwing side-arm (around and out to the side, almost like a Frisbee) you fling any liquid away from you.
It's also a good idea to make sure nobody is standing to your side that you could potentially douse in flames.
Happy tossing, and remember to only use this knowledge for educational purposes!