A. Draining though it is, it is normal that your son is into everything. It is so normal, you should be proud. It is wonderful that your son has the intellectual curiosity to want to explore and get into things. This is how he learns and it shows that he is a smart, growing boy who is interested in the world.
Try to find safe ways to help your son get what he needs. If he is constantly into the cupboard where you keep breakable dishes, move them and put empty plastic containers in their place. Is he always touching things that are forbidden? Move the tempting objects out of reach (or, even better, out of sight).
This leads to another important point: Choose your battles. For example, many toddlers love to rip up newspapers. Before you try to make him stop, think for a moment about why you don't want him doing it. Is it because of the mess? A certain amount of mess comes with the territory, and there's no way around that. Is it because you haven't read the paper yet? Then offer him a section you don't want. The point is, if you can't think of a good reason why your son shouldn't be doing something, perhaps there is no good reason. If an activity is harmless, it may be best to save up your authority for a time when there is something at stake, like his health (or the cat, or your furniture). If you're saying "no" all day long, neither of you will be very happy. Your job is not to show him who's boss, but to keep him safe, happy, and help him learn. Learn to let some things go.
When you do have to say no, be firm, calm, and consistent. Don't give in because he screams -- it will only encourage him to scream each time you say no. If you're going to give in, do it right away. Don't be afraid to use distraction to avoid a power struggle -- it is not spoiling to say, "Don't touch the lawn mower. Wow! Look at that airplane!" and whisk him away. The message is the same: The lawn mower is not to be touched. Don't let him play with the lawn mower one day because you're too tired to argue, because he won't understand why he can't play with it tomorrow.
Applaud your son's curiosity -- give him paints, or mud, or water to play with and let him experience the joy of discovery. If he sees that you enjoy it too, he will love learning. Let him know that you value his curiosity and drive, and he'll succeed in school. Encourage his energy -- run with him, climb with him, jump with him. He'll become a coordinated, athletic child. And he'll be happy because it will be something he shares with you.