[SanDog]

You won the first set 6-4.

Its 3-3 in the 2nd, your service game.

It's Ad your opponent, you serve, they weak return and your next shot forces them left, out behind the baseline.

Where do you position yourself for the return, and why?

It would depend on the skill level of my opponent, but most likely I would position myself mid court, at the net, expecting him to try to go cross court. A serious player could possibly hit the low percentage shot down the line, but I would take my chances at the net.