All from the elbow, get your body weight into the table and down on your leg as it comes in under the table. Forearm should essentially start parallel to the table, elbow slightly lower than bat. Important to remember never to straighten your arm too much and to be firm, a soft flick won't get you anywhere if it makes it over the net.
This video should be good for you, by WLQ
But I'm lazy to translate why his advise, could some one do it? lol
http://s.sohu.com/20120328/n339165990.shtml