Tip first
I generally mount the reel and pull out a bit of tippet so I can start rigging the rod when it is assembled. Then I start with the tip section and next lower section and work my way down to the butt section. That makes it easier for me to line up the guides than starting at the butt and working my way up to the tip.
I thread the entire leader and a foot or so of line through the stripper, then rest the butt end of the rod in a secure place, whether on the ground, the truck bed or seat, whatever. Then it is a matter of pulling enough line off the reel to thread through the remaining guides, staying clear of the blank and putting no pressure on it at any point.
The fish are always right.