My 3 older kids all went thru that around the same age. While I used words to let them know what I thought about their behavior, they were too young to really understand. So we used sign language and facial expressions a LOT to also get the point across. I don't know if all kids are like this, but my children respond to visual cues very well which is why the facial expressions seemed to help. Just today, one of my 21 month old girls was acting up. Instead of having to yell or scold, I just gave her "the look" and she immediately stopped and said "sorry". This comes in very handy at church, at the store or anywhere else that I don't want to be too disruptive.
Keep in mind, this doesn't work all the time. Your little boy is probably just getting to an age where he's trying to influence his environment and he's testing the waters to learn action/reaction. He's already figured out that there isn't much he can control. Right now I can't think of any suggestions on how to help him deal with that, but I know there must be things you can do. It's never too early to praise the positive behaviors so you can start with that. When my girls are behaving nicely, I make an exaggerated happy face and say "that makes Mommy very happy when you _____" (again with the visual and verbal cues).
Good luck with everything.