right now im currently doing 3-6 plank lifts 1 minute each and 200-400 crunches a day is this a good routine should i go on a certain diet to build help me build abs
I'm unfamiliar with plank lifts but I recommend these:
Leg toss: Exerciser lays on the ground, partner stands at their head, exerciser holds onto partners ankles, as the exerciser raises there legs up, the partner pushes them back to the ground. The partner can also push them to the side to work the obliques. Remember to keep your knees straight. You can do this with out a partner but to me it doesn't seem the same.
Flutter kick: Lay on the ground, place you hands together BELOW your buttocks (not under, but below as if your where standing up), raise both feet off the ground about 6 inches, keeping your knees straight, then kick them alternately as if you where walking. DO NOT rest your feet on the ground if you get tired, just raise them all the way up like you where doing the leg toss. Also keep your head up and look at your feet, its nearly pointless to even do the exercise if you head is lying on the ground.
Rocky Balboa sit-up: Just like the Italian Stallion does them

. Come up, rotate left then right, then go back down. Next time go right then left and so forth.
Crunches with a weight on your chest is also go. Anytime you can add resistance go for it. Plus you'll tire yourself out quicker, means you won't be doing crunches all day long.
Reps and sets are entirely up to you.
Many say you can work your abs every day, which makes sense to me. But that is up to you if you chose to or not. I however do not have "rock hard six-pack" but but I can do atleast 78 Sit-ups in 2 minutes and thats as high as the Army Physical fitness scale goes for my age group. So, now I'm working towards that "rock hard six-pack."
As for a diet "to build abs" I really can't help you there. I sure someone else could though.
EDIT: I just researched plank lifts, I've done those before but I don't see them being as effective as some I have just listed, but if you like them then by all means do them.