An oft-forgotten strategy is the chip-and charge play. Currently, when players do decide to come in on the opponent's serve, they tend to do so by thumping the return and sprinting in (and even these plays are few and far between). The chip-and-charge way is one of the cleverest ways to put pressure on the opponent when she is already serving under pressure. Unlike a "belt-and-bolt" (i.e., where you crush the return and then sprint in), the chip and charge, if executed correctly takes time away from your opponent since you are executing the stroke WHILE moving in. In addition, instead of risking that the opponent sticks her racket out to block your massive forehand return, against a chip she actually has to (1) move, (2) get down low, and (3) generate her own pace in order to pass you. All the while, you're rushing in and closing down the angles where she can go. 

To execute a good chip and charge play, it helps to be proficient at the slice. In this regard, it is important to understand that the chip (or the slice) is NOT A SWINGING stroke. That is, you don't try to swing at the ball as if you're cutting down a bamboo tree. You want to split forward, generate only a little pace with your shoulders (utilizing mostly the pace coming from the opponent), make contact out in front by leaning against the ball, and continue to follow the ball in a natural fashion. Practice this while your playing partner is working on her serves. Or, if you're working with a coach, practice this by having the coach serve to you and then feed a dipping volley. Remember, this is a shot that will pay huge dividends in pressure situation and you don't have to be a classic serve-and-volleyer to execute it correctly. It's the element of surprise that will win you the point. As long as you hit the ball deep (2-3 feet from the baseline) you will be in a great position to win - whether by putting the next volley away or by drawing outright errors from the opponent. Even if the opponent gets lucky and squeezes a passing shot by you, in her mind, she will always think that you're going to repeat the play and, as a result, put more pressure on herself next time around (and maybe you'll get a double fault). 

Initially, try to work on this play against weaker opponents in order to get the feel for how the ball should be struck and how you should follow the ball in. Then, against a better opponent, find a pressure situation where you can take advantage of her second serve and charge in "like the Russians to Berlin" (i.e.  FULLY COMMITTED to the cause; "d**n the torpedoes").