Some good conceptual advice in here already (IE, if you serve long and fast, your ready position after your serve should be at least half a step further back than normal in anticipation of the service return also coming back long and fast).
Here is another couple concepts that might help:
-practice your serve so that you have a serve that looks exactly the same but have two different types of spin (IE, one is a heavy backspin, the other variation that looks the same is top spin). Once you are able to do this, you can cause all sorts of problems with the serve returner. I like to start with a short back spin serve (and I know this will most likely come back as a push at my level). I do that a couple times, then eventually i switch it up to the top spin version. If i am deceptive enough, the top spin serve will be "pushed" back by the returner and the ball will pop up for an easy smash kill. Having the ability the deceptively change the spin of your serves will give you the advantage you are looking for.
-have a surprise serve that you can bust out at the opportune moment. if you can wait until you're up 10-8, that is going to really help if you can execute it perfectly. But if its looking dire in the match, don't be afraid to try it sooner. Just don't over due it. An example of a surprise serve would be instead of your forehand pendulum serve going across the table to your opponent's backhand, serve it fast down the line. You might get an ace or a horrible return to set you up for an easy smash.
And finally, here is one more strategy you might try using on a backhand serve:
-lined up on the right side of the table, do a short, underspin/sidepsin serve to your opponent's forehand. expect the return to come back to your forehand but also be prepared for the return to come down the line (to your empty backhand). The next serve is also going to be a backhand serve, but it will be long, fast with topspin down the line (to your opponents backhand). I did this strategy for a while and I got a lot of points. My opponents that I play regularly though have picked up on this tactic so i had to switch it up.
-also, you can try a pendulum serve short, with top spin to your opponents wide backhand. They will most likely push it or do a weak flip to your backhand. if you are athletic, you can pivot around the return and get nice loop down the line or back across the table. good opponents will be able to return this third ball, but you will be in a loop rally at this point and hopefully with the upperhand.