Early- when I open the pot, I limp in with low pairs, raise with medium and high pairs.
Mid - when I open all pairs are for a raise.
Late - same as mid
When it is opened before me
Early- call if I have the right pot odds
and implied odds with small and medium pairs, 3 bet or call with big pairs
Mid - try to 3bet if the stack sizes are right, fold if not with the small and medium pairs. 3bet or call with big pairs depending on my image and the opponents
Late - calling is usually wrong. 3bet or fold