How can i get my 2 year old son to listen when i say no?

Wow, this is the third answer from PinkPaisley that I completely disagree with. I understand your frustration. I've been there with a step child who definitely did not want to listen to me, but spanking is never the answer. It may seem to work right now out of shock, but please do not physically harm your baby. I can't understand why anyone would want to spank a baby who is not even 2 years old yet. That's laziness. It seems easy and you're angry so you're basically using your baby as your punching bag. The American Academy of Pediatrics does not recommend spanking and explain in this article why spanking is not a long term solution and does not actually work though it may seem to at first since the baby/child is in shock. AAP recommends no spanking and discusses why it doesn't work A child that age is not capable of manipulation though it may seem that way at times. No is not really an effective word I've found. It's too general. If your baby is getting into things that you do not want them getting in to. Take what they aren't supposed to have out of their hand and say not for (insert child's name here) Give them one of their toys and say this is (insert child's name here)'s. If that does not seem effective, make it impossible for him to have access to the things you don't want him playing with. 

for the record, my daughter has three chances to stop bad behavior before she gets a spanking. she's a very well behaved child, so it almost always clears up with the first chance. of course, she pushes the limits at times. she's a toddler. but she will learn that she's not going to do and say whatever she wants, and whenever she wants. there are rules, and there are consequenses when the rules are broken. when those consequenses lose their effect, you employ some stricter options.