[Mauvaise]

I'm only a 3.0 player so my strategy (such that it is) is probably different from others:

Against - Be calm, get the first serve in or get that return back no matter what, then play very "back to basics" tennis hitting fairly safe shots deep & up the middle until such time as my opponent(s) make the mistake or I get The Shot that I can safely and cleanly put away.

For - Much the same as above, except I try to trick myself into pretending it's match point against so I don't get cocky or stupid or relax too much.