We try to have simple rules around my house, real simple principles that can govern a lot of situations. The baby/toddler principles were this:

You can't say no to parents.
No throwing unless it's a game, and the other person wants to play.
No one can remember rule #3.
No one can remember this one either.

The new principles are coming out like this:

You are responsible for your own mess.
The dining room table is not a storage unit.
If it's not yours, ask.

We are also working on one kind of additional practice with the kids. They are getting frustrated a lot these days. So, when frustration mounts, particularly with something we are helping them with, my wife and I are trying to train them to say, "Thanks, but that's not how I want it."

We want them to say this instead of screaming.

It might be too much to ask, but if we don't start now, it'll just be terrible for the next 15 years of our lives.