The difference between recall / signs?

Right a total newbie question here.

Ok so very basically. I figure out what is regular in my dreams. For example it is often old deralict buildings for me. So this is my dream sign is it?

So how do I train my brain to recognise that "oh i'm in an old building, is this a dream?"

basically what you do is whenever you see an old building, train yourself to think, am i dreaming, and do a reality check, like look at your hand(it may have more or less fingers) or pinch your nose and see if you can still breathe. that way, it will become automatic for you to check whether you are dreaming whenever you see an old building, so when you see one in a dream you will recognize you are dreaming.
It's also a good idea to develop a habit of doing reality checks often so you continue that habit in your dreams regardless of an old building.
have fun and good luck :)