I don't move as fast as my mailman, so I've just left a stack of notes on the door for the past decade: If no one answers, please leave the package on the porch. If you need a signature saying you were authorized to do this, take a copy of this note (which has my signature on it). If that doesn't work, let the people next door sign it. If they're not home, let the people next to them sign it. If that still doesn't work, fuck it, I'll come to the post office.
I try to give them every option possible to just leave the thing there so I don't have to go anywhere to get it. Now they know me, so it's very rare they don't leave it on the porch, even if the shipping method specifically requires it. (Note: I am aware that I am surrendering some guarantees doing it this way. I don't have a problem with that.) The only time in recent memory that they took the stuff next door was when it was a couple of hundred dollars worth of computer stuff from NewEgg, who don't bother packaging larger items (like computer cases or even a power supply, once), they just slap a mailing sticker on it. It would have made for a very tempting pile of stuff on the porch.