Teaching to share - when and how?

At what age do you start teaching to share and how do you do it?

DS is 15 months old and has a little girlfriend next door to us (19 months).

Whenever they play together he grabs her toys and will not give them back. If I ask him to give it back to try or take it from him, he has a complete meltdown.

She, on the other hand, will nicely hand a toy to DS if her mom asks her to.

He does the same thing with his cousins.

What should I be doing at this age to encourage sharing?

Message edited 8/3/2009 11:07:28 AM.

Re: Teaching to share - when and how?

I think at that age the way to encourage sharing is by taking turns. Sharing in and of itself is too abstract a concept for a child that young to understand. DD is almost 20 months and she has been taking turns with almost everything since before she hit one year. (for example, before she could feed herself, I would give her a spoon of something, then say it was mommy's turn, then her turn etc - all the way through a meal).