Some good suggestions here, but before your head starts spinning more then your second serve, lets summarize although you'd have to be a genius or an idiot savant to learn to play tennis from a book or a message board:
1) Toss ball directly over the button on your hat which is called the "12:00 o'clock" position on the imaginary clock. (but don't wear a hat while you're competing, they just get in the way, unless it's a proper Ozzie tennis hat with a piece of cabbage under it, on a scorching day with babies crying in the background). If you're doing this properly the bicep on your tossing arm will touch your cheek for a reference point (palm facing up).
2) Speed of the swing does not change, same as for a first.
3) And here's the key: When first learning the second serve, to give you an idea of the feeling of "knifing" the shot, hit the ball with the edge of your racket--and I do mean LITERALLY with the EDGE of your racket! Don't do this where infants or adults could be injured! The best place would be an open freshly harvested cornfield near Smith Center, Kansas, where no one will be watching to embarrass you or be injured--or alternatively on the outdoor roof-top courts of an urban tennis club where when the ball goes flying out to the intersection below you may hit the windshield of a passing Mercedes and cause a wreck--then run into a shower-stall and hide 'til the cops and the ambulance chasers leave.
4) Now hit 1,000,000 practice balls.
"...the human emotional system was not designed to endure the mental rigors of a tennis match." Dr. Allen Fox
Last edited by tennis tom; 11-28-2012 at 07:49 AM.