For me this was not something that just naturaly happens.
First let me say that you don't even need to worry about this if you do not have a consistant toss and a high and I mean high toss.
Now after all that you can pretty much take your time and get your body how you want.
I personally have to toss with weight on back foot a begining and then on front bowing with arm pointed all the way up bringing racket up, that is the trophy.
After this you are ready to let that racket drop and relax, the racket drop and then once it drops down you turn the body, should and snap up.
Once you get this the serve will feel so easy.
You can get even more if you keep the toss right above the head.