How Do You Teach Sharing?

It seems there are two ways a parent can attempt teach her child to share.

1. While playing with the child, the child comes to take all of the parent's toys, leaving the parent with nothing. The parent can refuse to give all her toys away, thus giving the child a real-world example of when to share and teaching the child that she cannot have everything she wants and must share with others.
   
   Or...
   
   
2. While playing with the child, the child comes to take all of the parent's toys, leaving the parent with nothing. The parent can freely give the toys to the child, showing by example what sharing looks like.

Which way would teach a 20 month old the correct concept of sharing? I feel that in #1, I am teaching her selfishness, but in #2 I am teaching her that she can get her way everytime.

In case you couldn't tell, there was an instance recently where I had to decide which path to take. Olivia and I were playing with dixie cups. She loves the fact that they stack into each other. But she wouldn't let me have any. (I wanted to try speed stacking)

She kept trying to take them away from me and I attempted to teach her to share using method #1. This resulted in a half an hour temper of tantrums as she kept trying to come and sneak my cups away from me.

Then I came to the realization that there are two possible ways to teach sharing and that I might possibly be teaching selfishness with this technique. So I switched over to method #2. But I only gave her half of my cups. I told her, "I'm going to share my cups with you." "Would you like me to share my cups?" Well, she gladly took what I was sharing, and then screamed for the rest. She even tried bartering. She came up with a book and offered it to me. Then tried to take my cups. She brought me my tea (it was luke warm and half-empty, don't go calling DCFS). While I was thanking her, she tried to take my cups.

So there I am, sitting on the couch, holding my remaining three dixie cups (along with a book and a mug of half-empty tea), and praying to God for direction and wisdom.

Oh, and Olivia is screaming and crying throughout this whole process.

And then I switched whole-heartedly over to method #2. I asked, "Would you like me to share my cups?" And then I gave her my last three cups. And she smiled. Her collection was complete. (Humming the song from the Little Mermaid now...). And I'm left there wondering if I did the right thing.

I come over here to blog my dilemna and Olivia calls out to me. She wants to share her cups with me! She would give me half her stack and then take them back one at a time to stack into her one big pile. Then she would give me half again and repeat the process. Each time she gave me some of her cups, I would exclaim, "Thank you! You're sharing with me!" Eventually, everytime she gave me half her cups, she would stop and applaud herself for her good deeds.

So I don't know if it was one method in particular or a combination of all of them, but I think we might have learned something here today...