I need help building up core and six pack.?

Getting a six-pack in a hurry is going to require some sweat. Crunches are good, but traditional sit-ups are better. Proper form in each is key. Use a yoga mat or exercise mat for cushioning on the floor.

Exercise Ball Crunch - For this exercise, an exercise ball is necessary. In this routine, the abdomen does more exerting but will still need the entire body to stabilize it throughout the routine. To do this exercise, lie on the ball with your lower back fully supported.

Eat lots of lean protein. Beans, nuts, and lean meat are rather good for you as long as you do not eat the fat!

Drink water. You should replace all your regular beverages with water, especially soda and sugared drinks. Water will make it easier to lose weight. Consider flavored water as an alternative if you must.