E.I.
well.... i wouldnt totally count on the idea that he understands what you say.
we adults have a way of talking that really hurts our chances of making sense to our children. mostly, use of contrations like cant and dont... kids will not understand those words. use other words like stop, or no, or wait, or just do not or can not.
also, never ask your child to do something he is required to do. dont say "would you like to pick up toys" when he should pick them up. tell him "time to pick up your toys". never add "okay?" to the end of any required action, that also implies they have a choice. and though we shuld thank our kids for being extra helpful, saying thank you to a required action is giving them the impression that they had a choice in the matter. instead compliment him on the way he did it "i liked how you picked those cars up and put them on your shelf so nicely" instead of a thank you.
again, he still might be a little young to really understand any of that even. :P dont expect more of your son than he can really preform. dont think hes stupid or anything, but dont expect more than he can really do. i dont know...
also, if he knows it gets a reaction out of you, he will keep doing it, especially if he gets his way. what i would do is within reason, just look away, walk away, do something that shows complete ignorance of his behavior, even when it makes you want to scream. this shows that you are, in fact, in control and since negative attention is still attention, any response from you is going to motivate him even more.
distraction is a good key thing with kids. if you are in a public place, you cant just walk away from your kid, and there is a social need to get your child to stop spazzing out. get a book, a menu, a toy, a billboard, an ad, a pen and paper, a sugar packet, stack creamers, anything you can do to distract him from his anger and get him thinking about something else is good. try some teething remedies, as this is a common age to start getting molars, and those suckers HURT! as a mom who is getting wisdom teeth in, i have a good idea of why teething babies are so cranky ! it friggin hurts!!
anyway, just do the best you can. the more you listen and respond to his cries in a loving way, the more easier it makes understanding the next cry. however, the more you ignore tantrums, the more they go away. you have to know the difference is all. and you have to trust yourself to know the answers for you kid, not anyone else.