Jerk. Hopefully it was a joke.
In my opinion the key is actually to avoid the temptation to alter your play and instead play how you normally play; if you do so, you have the best shot of performing near your rating, and in doing so you should be able to count on beating someone performing at a much lower level.
It's simple really. just drag them kicking and screaming into and endgame. Then, when they're just starting to accept the fact that they will have to engage in that battle of "whoever promotes their pawn first wins", you back rank checkmate them (usally with a lot of sacs to lure them in.
Here's an example: