In my experience shared dreaming doesn't work the way people think it does. It isn't a realtime shared experience, but rather what's known as dream telepathy. To understand it, you need to keep in mind the way the subconscious works. It's always running, except maybe when you're in the deepest levels of sleep, but when you're awake it runs on the backchannel so to speak. I liken it to the stars, which are always there but in the day the sun is so bright you can't see them. So with that in mind, dream telepathy works like this:

Two or more people share a telepathic experience. They don't need to be asleep at the time, and I don't know why or how it happens, but a group of thoughts and feelings seems to make itself known to them all. It seems it needs to be processed while you're sleeping, just as much of your normal waking thought processes do (that's largely what dreams are). So the shared telepathic experience remains quietly in the background until you're dreaming, at which time it expresses itself in your own terms and imagery.

What I mean is that each person won't dream exactly the same thing, and they can't really talk to each other or anything, not in 'realtime' or interactively. Instead, just as dreams do normally, they will dip into your memories and ideas to create appropriate images. For example, if a doorway is important symbolically to the experience, one might dream of a particular door they've seen before, while the other might see it as a cave entrance or the front door of their own house.

The way you discover that you shared a dream telepathy with someone is to discuss your dreams with people - which is a big part of what DreamViews is about of course. People can read each other's dreams in the Dream Journal section, and sometimes you'll find that one or more people had dreams very similar in some ways to yours.

Of course, as with all subjective phenomena, some people have pre-determined ideas of how they think it should work, or they have a fantasy that they think would be really cool, and shared dreaming seems to be one of the things people have rather weird ideas about. People love the idea that it can be a realtime interactive experience, so many people refuse to even entertain any other possibility. While it doesn't seem to work that way, there is still a very strong sense of contacting an intelligence when it happens. The other person seems to be more 'real' than normal dream characters, even if they're presented cartoonishly or very strangely in the dream.