2 year old tantrum!

My son, whom is 2 has decided that his new "thing" is telling me NO! I would tell him to do something and he would yell no! I would hand him his cuppie and he would throw it and say no. When we go out in public, OMG!! I don't even wanna go there! It's not as bad as it could be, I keep telling myself. And he is really calm, and listens to me decently for a 2 year old. He seen his cousin who is also 2, tell his parents no and he don't get in trouble for it. But Jace does it and he gets in trouble. Can I please have some advice!!! I don't want my kid to be the kid no one wants to be around or the kid at Walmart throwing a fit because he doesn't get his way... I need to know I'm not alone!! Lol