Counter attacking Football, or even Defensive Football if you're heavily outmatched talent wise has often worked for me.
My mid-table Belgian team Charleroi took down Anderlecht with good counter attacking Football. If you try and play a bigger team at their own game, you're gonna get played off the park. I find if you play too defensive and let them come at you time and time again, usually they'll sneak a goal or two, even if it takes them a while. Playing counter attacking is still using a defensive philosophy, but still offers an attacking threat when the few opportunities arise.
Captain Obvious I know.
But stating what has worked for me, not just in my Charleroi save, but others too.
Team talks I find can be useful too. When the odds are heavily against you, I often say in a calm manner something along the lines of just go out there and enjoy yourself.