A quick bit of searching via google leads to
http://en.wikipedia.org/wiki/Apple_DOS#Boot_loader the text of which suggests that having a BASIC program file named "HELLO" might suffice for an automatic start with stock DOS. I don't know if it would work for a binary program. You could also patch the DOS image on the disk to load a different file, or if you're going to be working in assembler anyway you might go with a substantially customized startup procedure.
It's been a while since I've done any serious apple2 work, so I'm more than a bit rusty on the details, I'm afraid. I should have access to some of my old manuals in about a week, though.