Color correction workflow
I am not an experienced colorist but I believe I can provide you with some answers. At least from an indie filmmaker's point of view.


Wait until you have the final cut (or lock-off cut) before you grade. Grading usually happens at the same time as the sound design as both require a locked-off cut. It is best to wait until this stage so that you don't have to go back and grade new shots if the director decides he/she wants to make a change.
Correct individual clips on the timeline. You said you grade in Premiere using a plugin. That's cool. But there are other options. I always went from Final Cut to Apple Color but have recently discovered DaVinci Resolve. The Lite version is free. Here is a bit of info on it.
Grading clip by clip is the best way to go because you can see what the clip before looked like and so you know what the next one needs to look like, i.e. it's easier to reference. 
You don't want to color grade the original video incase you decide you want to change something later. I believe doing something like that is called destructive editing. You want to keep it raw so that you can always come back to it. 
In my experience, no, it happens at the same time. 
Not too sure about this one. Avid Media Composer has pretty good color grading capabilities, I never use the auto correct on it, but it's there if you need it. Check out this tutorial on grading in Avid. Other editing programs may have similar features, but I personally don't use them. And if you're editing a film, I don't see why you would want to.
Yes there are things you can do to help with grading in post. That color chart you linked to wouldn't really help you. I think that's more for when people shoot on film. They shoot 10 seconds or so of color chart on every new reel of film to make sure that the people who are processing their film are consistent. So, they have the same color chart and the same film. Provided they shoot it with the same lighting and exposure, the color charts should all look exactly the same when they come back from processing and telecine. If they don't the film processing company can get into trouble. 
During production you pretty much want to make sure you get the flattest image possible and correct exposure. If you under or overexpose a part of the scene, there is no detail recorded and there is no way to get it back. If you shoot on Canon DSLR there is a great (free) picture profile which helps to obtain a flat image optimized for color grading. It's called CineStyle by Technicolor. Otherwise you can shoot with the neutral picture profile with the contrast turned all the way down. 
I only have experience with Canon DSLRs so if you are using something else you would need to do some research on how to achieve a flat image.