The advantage of producing an accurate low serve cannot be over emphasised. A serve that passes low over the net immediately puts pressure on the opposition to either attack early or invariably forces a lift where the serving side can immediately go on the attack.
A serving partner in doubles play should stay at the net following a low serve to reply to any net return whilst their partner takes up a more central mid/rear position to cover mid/rear replies on either backhand or forehand sides.
Key points of a low forehand serve are:-
Follow serve with racket up ready to attack any net return and reply with net shot, drive, kill or net lift.
Watch this video narrated by Gail Emms concerning the forehand low serve.
Remember that in doubles a good low serve can set up your partner to attack lifted replies.