For those light hearted comments above about "how easy" "how obvious" "how fun to play with the controls" "I thnk this is how you do it":
The rudder pedal with the most resistance will be the one to push I think
Further down the line, putting the stick forward while maintaining in-spin rudder can be good fun
might I suggest a read of this (recent)
AAIB Report and associated references.
To the OP
What is the most reliable way to know in which sense to initiate recovery?
read the POH and listen to/ask the instructor in your training. It will be somewhat type specific
NoD