A good diet and low intensity cardio a few times a week.
I wouldn't suggest training abs if you want that V/X taper as your obliques will grow along with your abs.. squatting and deadlifting should be enough.
BUT here's are three sample routines I used to do before I realized that..
Weighted Decline Crunches 3x8
Hanging knee raises 3x12
Stomach Vacuums 10minutes
or
Windshield wipers 3x6
Weighted Planks 3x3-5minutes
Delcine crunches 1xfailure
or
Roman chair sit ups 5 minutes
Weighted decline twists 12x3
Captain's chair knee raises 3x12
But remember if you have a good amount of fat over your abs, making them bigger is only going to make your gut look bigger.. diet is key when you want abs.