Hi, We also had this same question in mind when we started producing automotive components. Apart from all the good advice on WHAT both
APQP and PPAPs are, we learned some valuable lessons. My ramblings may not be as others see it, but rather my own observations on the question at hand.
APQP is the planning phase. Do not try to do this AFTER you have started production purely as a paper excercise because it is a requirement. Do it upfront. APQP is the part where you plan out your program. Involve EVERYONE. Well planned is half the job done successfully. At this point you will almost be looking at a crystal ball, or tarot cards - here in africa we may get a witch doctor to throw the bones. You are looking at what the customer wants, then planning the product build and robust process. We learnt that long involved and complicated process routes cost time and money. KISS.
You will also be looking at DFMEAs and control plans. There are alot of posts on these. Initially you are looking at what may go wrong, and controls for prevention and detection. DO NOT kid yourself that the process is such that nothing will go wrong and that your controls are brilliant. Continually improve wherever possible. Murphy the lawyer, and author of the rule Murphys law is active always. Your prototype is important too. If you do a quick fix to get the prototype out, you have failed before you start. Be wary of cost all the way upto this point as bad design of product or process can cost you dearly. Important too is GIVE THE CUSTOMER WHAT HE WANTED - his spec is law.
So, onto the PPAP. PPAPs are not a "part time" job and are not meant to be done because the system says so. They are invaluable documentary evidence that the part conforms to the specification, that you process is stable, and capable. It is good evidence that you are compliant, and as a living document will tell you when you are going wrong. It is important to determine what level of PPAP submission is required - this will influence the content of the PPAP. If APQP was done well, the PPAP will be easy to compile.
A final word on this - if you need to put your part into the IMDS database, get some help. We had a few issues completing the IMDS statement.
Good luck