There is one serve that will keep you in the point against almost anyone. It is a very short, low serve that you vary between a little underspin, and no spin. If you can conceal the spin at all well, even world-ranked players will treat it with respect and usually just drop the return back short.
The reason this serve works is because it creates uncertainty for the receiver, and denies him the spin he needs to make a strong shot. Top players actually use your service spin against you to help control where they want the return to go. But a lightly spun serve poses a problem, because the amount of spin is hard to read — and if he misreads a no-spin, the returner will pop the ball up a little and lose the point immediately against top competition. Hence, you will usually get a little dink back. By contrast, if you crank up the spin, the receiver will more easily read it (because of the bigger motion you make), and can count on at least some of the advertized spin being on the ball even if the amount is misread.
Of course, it’s no easy trick to attack a world-class dink, but at least the point isn’t over (in doubles, especially).