Decide the nature of the task. If you are out to put a new finish on the car, this process can go as far as complete disassembly, taking the panels down to bare metal (and welding in replacement material for any rust) and going foreword from there.
The web offers a lot of excellent resources in this process. If you take the time to look around, you can probably find a procedural guideline for virtually everything you’re going to encounter.
As implied above, the majority of work and time is in restoring the underlying surface to pristine condition, or as close as you wanna get to it.
Another element not mentioned above is the need for fireproofing the work and especially paint areas and for a really really really good exhaust system. Oh yes, and you have to devise a way of maintaining a high air flow while keeping the volume of dust particles to a bare minimum. There are actually painting tools to do all of this, of course.
Last, there are a lot of excellent chemical paint strippers on the market. If you are going to redo entire panels (advised), using a chemical stripper will leave the metal in far better shape than grinding away paint with a sander, plus it will only take about 1/100th of the time.
Mostly have fun with it!
'00 ML320 "Casper"
'92 400E "Stella"