Do all four at once and then wait. I'd be surprised if there are many who suggest one at a time.

Doing one per month will let the 4th app see all 3 prior credit pulls and you will likely have a lower score in that 4th month than you do today. Do all four at once, get them all, take the score hit and then wait for inquiries to go away. Also, waiting for one inquiry per month to drop off your credit report in a couple years would annoy me.

Four is a little low though. I usually shoot for at least 6, and I think that might even be low for most who do real app-o-ramas.

Always being ready for the big score is a concern for all. I just don't do AOR's until there are a couple huge offers out there.