add an input parameter named @Debug = 0 (defaulted to 0 = off) at the end of the parameter list for the procedure.
then add if (@Debug = 1) print '...';
statements in the code at key junctures to display any useful internal values etc.
Yes, it's "old school" and debuggers that let you "walk the code" are great - but this works for anyone from any SQL tool (including anyone debugging without your same IDE).