The shot before the volley is the most important shot. If you serve and volley, make sure you have a good serve regarding placement. Know the most likely replies to each serve you hit (out wide, down the T, etc.) and get in position to increase your odds by making the next shot even harder for the opponent. Dont look to end the point after your serve. Look to end the point after your first volley.
Your serve is used to produce a weak reply or a neutral reply. Your first volley is designed to get the opponent off balance or on the run for your putaway.
Obviously, if it is real weak then put it away after your serve.
Know the add court and duece court possible replies to your serve in different areas of the box that you serve to and which are the returners high percentage choices. Be in position for those and let them have the low percentage choice.
Like Momo said, if you get passed, pick up the ball and deal again. pressure can be a killer as the match progresses.
Former USPTA Teaching Professional
Volkl Tour 10 V-Engine Mid/Luxilon Big Banger