I agree with RichardRimes. There are too many unknowns for a simple answer. Some people go for a high reward/risk ratio, in which case they generally say you never adjust. I prefer a lower risk, so I go farther OTM. If one leg gets threatened, I may roll it out and double my position, aiming for break-even. It depends on time left and where I think support/resistance are.
Resist the temptation to put on a new trade on the other leg to make up for the loser (i.e., if your put leg is in trouble, don't open a call leg). If the market snaps back a little, the calls would be threatened quickly and you'll be in the same (sinking) boat.