Share the best rules for our Kids

Hi ladies;
This week my mind is around the subject: rules for kids. My kids are 3 and i'm beggining to feel the need to make them understand that are rules and routines to follow. I thoght i could learn from all of you and it would be nice to learn from eachother! Now it's difficult for me to handle them!
So, what rules do you try your kids to understand and at what ages?
For example, now (age 3) i'm finding important :
- to teach my kids to put the toys back in their place before doing another thing (like going to bed or dinner)
- to understand that they can't have a snack after 6 pm
- if they don't eat enough veggies and protein they can't have desert
- they must say thanks
- they shouldn't speak loud...

Thanks in advance