I hope you folks could put these observations to the test.
1. God given dreams seem more vivid, visually speaking. Probably something to do with the source being spiritual instead of just being from our imaginations.
2. Does the narrative of the dream follow events or thoughts from your everyday life or the past? If so its probably not from God, but normal processes of your brain. God is creative, his dreams are going to be original.
3. Lots of imparted knowledge? Details that would not be obvious are given in the dream.
4. Is it Memorable? It should have a greater impact on us and not be forgotten a few minutes after we wake like is the case for most dreams.
Oops! Missed another one.
1. Mmm... iffy... not really actually. I have received short visions and dreams during sleep that were very dim and made little impression on the brain, and found myself having to really struggle to remember what they were. But I found out the reason why: They were things I was NOT red hot about hearing, and when He knows that He has to tell you something you don't want to hear He has a way of making you really have to listen close, or in other words
want it first. So on this one, I'd say it's not a hard and fast rule no. That doesn't mean that there won't be others that are extremely clear and virtually unforgettable. Sometimes the symbolism is so creative and the imagery is so vivid and clear that the Spirit will bring it back to you twenty years later and it's as crystal clear as ever. That's the power of imprinting images on the mind. A picture paints a thousand words, and a short dream can paint thousands upon thousands.
2. ABSOLUTELY. He enjoys being creative actually. It's as if He's a painter, creating especially for your situation, almost like if you had a street artist paint you in the moment.
3. The details are everything. Drives me bananas when I do an interpretation for someone and then they say, "But how does that explain the ..." and go on to list some detail they they FORGOT to mention.

I have literally seen one little detail, actually mentioned by the person this time that I missed, change the interpretation COMPLETELY, like 180 degrees in the exact opposite direction. Every detail is placed there for a reason, and needs to be accounted for.
4. Heavens, yes. This is usually one of the keys for me. Did it wake them up from a sound sleep? Has it been bothering them ever since they had it? Is it something the Spirit has brought back to their memory, even though they had it years and even decades ago? If it is of God you won't forget it.