If there is a particular toy that is causing a lot of squabbling, I just remove it when no one is playing with it. For the most part, my guys don't fight over toys too much, although they do have two of a lot of things (everything from my mom--who also happens to supply most of their toys). They know to go and get "the other one" if they want a toy that their brother has. It's actually their most favorite thing to play with the same thing at the same time (and I was really hesitant to allow two of the same thing, so this was surprising to me). It's like they both enjoy their toy more when they see that their brother is also playing with the same toy.
I pretty much DON'T intervene when my guys are doing the occassional tug-of-war, and because I never have, they don't really look to me to figure it out. 90% of the time, they are able to resolve things without tears. The other 10% of the time, I'll find another just-as-exciting object for whoever is left upset. If I noticed that one twin was always doing the taking, or always ending up with the desired object, I'd probably step in more. But it seems to be pretty balanced, so I'm staying out of it for now.
I like that I am not a referee and that my kids already know something about working things out on their own. They are just about 15 months old now, and get along really well most of the time. So, things could still change for us as we get further into the toddler years.