If you have to referee sibling conflicts on a regular basis (and most parents of more than one child do), you should have a game plan.
(1) Don't automatically dismiss your child's anger. Instead, it is important that you recognize your child is upset, whether he has a legitimate right to be or not.
(2) Don't promote guilt. You don't want to force your child to act a certain way out of guilt. It is much better and more productive if you help them resolve any conflicts that may arise.
(3) Do give your children an opportunity to handle their disagreements without interference from you. Often, children begin arguments and fights simply to get attention from their parents. Step back and see if your children can resolve their conflicting issues. Don't instantly jump into every argument. If you can ignore them for a little while, they may settle the problem without your help.
(4) Do look for ways to ward off confrontations. For example, if you know your children are going to fight about who will get the first piece of cake, have a system in place. One suggestion might be to let each child take turns being first for a whole day.
(5) Do use positive reinforcement. When you see appropriate and good behavior out of your children, let them know it! Praise is an excellent behavior management tool, so don't be afraid to dish out the compliments!
Consequences
Finally, it is important that your children realize there are consequences for both good and bad behavior. You need to come up with a fair system of punishments and rewards and, above all, be consistent. Some parents have found success stopping those constant disagreements by simply punishing everyone involved. This would certainly cut down on repetitive tattle tales! You should also come up with ways to reward good behavior.