How can you tell a first printing of Hokuto no Ken?
A first printing of a Hokuto no Ken tankōbon is a Shueisha Jump Comics book from the original run, and the edition system makes fakes of identity easy to avoid: every later edition says so on its spine. The aizōban (1991 to 1992) and bunkoban (1997 to 1998) are 15-volume Shueisha sets; the kanzenban is Shogakukan, 14 volumes, 2006; the Kyūkyokuban is Tokuma Shoten, 18 volumes, 2013 to 2014, with visibly new cover paintings. If the book in hand is not a 27-series Jump Comics volume, it is a reprint edition by definition, whatever its printing.
Within the Jump Comics run, check the ISBN block: volumes 1 to 20 carry the sequence 4-08-851661-3 to 4-08-851680-X, volumes 21 to 27 the sequence 4-08-851824-1 to 4-08-851830-6. Then read the colophon (the printing notice at the back): a first printing’s first-printing date matches the volume’s release date, which for this series is documented to the day, from March 9, 1984 for volume 1 to March 10, 1989 for volume 27. Later Jump Comics printings keep the ISBN but advance the printing date.
Condition of the package matters to value as much as the printing line: the obi, the paper band around the dust jacket, survives on a minority of copies and is the first thing the market asks about after the printing itself.