I really disliked the advice in Siblings without Rivalry. I read it when the twins were probably 6 (they're 10 now), but some of the advice was to let your children say they hate each other. That's not OK with me. Much of the other advice was to stay out of their fights. I agree with that in principal, but when kids are little, it's important to explain to them how to handle disagreements. I'm sure there's good stuff in the book, but the advice I disagree with sticks with me because it seemed so fundamental to the book's philosophy. Anyway.. just my 2 cents.
Some things we've done with our twins boys and dd, who is 3 1/2 years younger:
-- putting them in charge of each other at the same time-- and making sure the other one is happy.
-- Making them do mitzvahs (good deeds) if they hurt the other. (This worked really well when they were 4-6 or so.)
-- If they were fighting I sometimes had them literally kiss and make up. This always made my boys crack up, and dissolved the tension.
-- Giving them each a "favor" that they have to do for the other child at any time during the day.
- Having them help each other with something
-- having them teach each other something
-- Interrupting arguments and explaining the "right way" to handle something, i.e., "if Johnny is playing with a toy and you want it, ask him when he'll be finished with it so you can have a turn. We don't grab toys." "If sister isn't listening to you, you can come to me or walk away, but you can't yell at her," and on and on.
Follow Mothering