Best Ab Workout. PLease help!?

Yeah im 15 and im not one of the ignorant people that are like
I WANT ABS IN 1 WEEK TELL ME HOW!!@!@!

I am looking to get a big gain in abdominal muscle in about 4 months.
If someone could give me a good ab workout that i can do every other day that would be excellent. I have protein shakes at home if i should take those. ANYTHING that will help me get the most effective workout will help. Thanks!