There is, I'm afraid, no strategy available which overcomes, or even neutralises, large disparities of ability in chess. If you find one, bottle it - because it'll make you a millionaire
Greenpawn has it about right - play classical chess by putting your pieces on good squares, and avoid creating weaknesses, especially by unnecessary pawn moves. Highly-rated players are rarely bothered about flashy attacks. Why risk getting it wrong when the other guy will make a mistake soon enough? So we wait, and wait.
But occasionally, as Mahout rightly says, we get it wrong. The causes of this rarely have much to do with one's opponent though. We are more than capable of turning a position into a squashed banana without any help from our opponent. Complacency, lack of attention, game overload are all factors in this. However, one caution: a highly-rated player may stumble into a 'lost' position; but the lower-rated player still has to win it.
For example, take this game of mine recently. Until White plays Nf3-d2, I'm pretty much dead. I've played sloppily, and deserve to be squashed. Indeed Nf3-d2 is a plausible-looking move. But it's fatally flawed - and against a highly-rated player, you won't be given a second chance. So after Bxg2, White gets trounced instead.
Now another game, my worst-ever loss - with a 1000pt rating gap
I'm not sure it was quite that wide at the time, but no matter - it was plenty wide enough. My Bg5 is bad; my Bh4 is just dreadful - played lazily and without thought. Even so, I remember thinking: Black may not see the win if I complicate a bit. So I sac'd the N. Alas for me, B wasn't distracted. See for yourself here, and laugh out loud