what is your routine for abs/core?

none, change ur diet. auto-six packs.

Front squats, ab rollout, DB hanging knee raise "good luck", planks.

Banded pallof presses are my favorite though.. Usually do a medium band with a huge rep range, like 5 sets of 20 with some 5 second static holds during them.

i like to take a permanent marker, and draw an 8 pack. typically ill do 1 set per every 2 weeks. depending how much you shower or are exposed to water you may need to increase set/ rep. but results are immediate