Efficient way to determine line and load
Your method is safe, albeit tedious. Stick with it if the following doesn't match your comfort level.

But if you're willing to boost your risk level a bit, leave the outlet hanging on its wires outside the box and have a radio or light plugged in that indicates current without you having to touch anything. Be careful of course that the two connected wires aren't touching anything other than the outlet. For maximum safety, don't touch the outlet when it's hanging out of the box and the breaker is on. Don't do this if there are people or pets around that don't follow instructions.

If you don't have one already, a non-contact voltage detector is a good thing to have. It'll tell you quickly if a wire is hot. I like my Fluke http://www.amazon.com/Fluke-1AC-A1-II-VoltAlert-Non-Contact-Voltage/dp/B000EJ332O but there are cheaper ones at the big box stores. (Cheaper might also mean less reliable... I haven't tested that theory.) The only bad thing about these is that you'll occasionally get false positives and have to dig out your multimeter to know for sure what's going on.