Hi Sara.Backhand serve is my favourite. I have done many direct points with it. It is most effective when the match is starting. Here are some tips. Stand on toes - it improves the vertical angle. Keep shuttle very close (1cm) to racket head and do not do any movements that would signal to your oponent that the serve starts the next second. Do not make back and forward movement with the racket when starting to serve. Start with forward racket movement. Use just your wrist. Adjust the horizontal angle of the serve in the very last moment. Do not gaze at the place where you expect your serve to land. And last but not least - practise, practise, practise...
I agree with most of trapped-never's comments but have some reservations. The object of tha backhand serve is to produce a reliable movement, same as every other shot. In order to do this you must eliminate any possible variables. Standing on toes may give you the extra inch or so but only do this if you are very well balances or a slight change in angle may compromise your serve. Using your wrist works very well but just using you elbow works equally well. The important thing is that you only use one joint to reduce variation in the swing. Also you should point the shuttle towards the racquet, the same every time, to increase accuracy. And yes, practice, practice, practice.
I would add one personal reservation to trapped-never's description. He/she wrote that you should only have a forward movement. I understand the reasoning behind this, but when I coach others I find that most people achive a more reliable shot by starting with the racket and the birdie touching eachother thus making it necessary with a slight backward movement before the forward movement. As Slanter also points out, the objective is to reach a reliable shot by eliminating all variables and a lot of people seem to find it hard to begin the motion at the same place everytime unless they start with the racket and the birdie touching eachother. .
Stance A few words on the stance: Most common is to stand slightly sideways, with your racquet foot in front (place it at the "T" if you are playing doubles, but perhaps 50 cm further back if it's singles). For a short backhand serve, you want the shuttle to spend as little time in the air as possible. You achieve this by keeping it low to the net, and leaning forward slightly when you serve. Hold the shuttle out well in front of you, not close to your body. Mind you, if you look at top players there are a lot of variants of the backhand serve stance. Some stand with both feet parallell (especially in singles), and yet others stand sideways with the none-racquet foot in front. There is no right or wrong, do what feel most confortable for you. But I would start out using the first variant.
Re: Stance Regarding the stance, notice that some players s"witch the feet" by always keeping the foot close to the middle out in front. I don't know why this is.
A good tip is to push the shuttle and not hit the shuttle over the net. well a good way for practising is get a tube of shuttles place it on the opposite T and try to knock it over (oh and have alot of shuttles ready as it saves time trying to go round to pick it up) hehe The pro players now even pay attention to how they hold the shuttle (horizantally) which aids the flight to not be as high (Tony Gunawan is an example). Remember serve with your right foot if your right handed. Low serve is preferred but only serve high if you have to as the lift in doubles means the opposing player gets the opportunity to smash first (only in doubles)