I do the lines before the legs because i work in the same direction whether dropping off or picking up.
By starting at the clip (connecting) and ending at the clip (dropping) and going anti clockwise with number plate in hand, nothing gets missed, ever.
If i get interrupted i start again.
What gets my goat is those who fail to use the air suspension on the tractor correctly both times, not only to save the landing legs from unnecessary strain but to keep the fifth wheel grease (especially on a newly greased plate) where it belongs and to ensure they don’t overshoot the pin.
Our trainer doesn’t mind which way you do it so long as the procedure is safe, he doesn’t hold with making people change their methods unless he spots something idiotic, ie like those who attempt to unclip and pull the pin first, that’s a failed assessment and cheerio.