First off, do cardio to burn off any extra weight/fat.
Second do a variety of ab exercises, variety is key to building all those different muscles in your abs.
Do cardio one day, ab exercises the next and so on, Also, give yourself a day to rest each week.
Try to eat six small meals a day. Your plate should look like this : 1/4 lean meat, 1/4 whole grain and 1/2 vegetable/fruit. Also aim for eight glasses of water a day!
Good Luck!