Alternative Reality Checks
I came up with 2 RC ideas now. I'll be trying them and I'd like if someone else also tries. New ideas, improvements are welcomed too.
1) Nose RC: Try to see your nose. We can see a part of our nose but it's usually something we don't pay attention to and I don't remember seeing my nose in my dreams (like a movie). So this might work.
2) Question RC: I'll be asking this several times a day: "Is this a dream?" expecting dream/objects/someone to answer. Since there are endless possible answers which are most likely unlogical this could be a good sign.