I vacuum first, then I clean the carpets.
I clean the door jams, trim and anything else next, followed by treating the trim.
Then I do the windows, outside first.
If the seats are leather, then I do them last so if I sit or lean on them I don't re-dirty them.
I finish by quickly vacuuming again to get any dirt or crap that I dropped while cleaning the dash/trim/etc.
Of course I give the carpets some pretty lines in them to put the final touch.
I think the only important thing in my order is cleaning the windows after dressing the trim b/c of how easy it is to get some on the glass.