Usually, a good under-spin serve is a good way to start a point, because it can force the receiver to push the ball back, yielding the server the option to attack. A good flip shot can turn this usually safe serve into a dangerous choice, because the receiver immediately grabs the offensive.
Step in with the table tennis paddle open and raise the hand a little over the intended contact point. After the ping pong ball bounces, lower your hand and with a sort of scooping motion, play the ball, contacting it on its lower portion and then turn the racket over to project the ball over the net.
Make sure you keep your body in solid balance, and give the ball enough forward motion. The success of this shot depends very much on your confidence. You cannot hold back or you'll drop it into the table tennis net.