A dream sign is just something that you tend to dream about a lot, so it's different for everyone. For example, I often dream about the house I grew up in, so I try to condition myself to associate that house with dreaming. When I find myself in the house, I must be dreaming. Ideally, if I can always remember that, I should realize I'm dreaming whenever it happens.

My other dream signs are old rotary phones (especially if they have too many numbers on them!), my father, and UFOs.

The reality check is just confirming for yourself that you are awake. If you fail the check, it naturally means you're asleep! My usual check is to read something, look away, then try to read it again. If I have trouble reading, or if the words change, I am dreaming.

I actually posted a yellow sticky note on the wall of my cubicle at work which has in bold hot-pink highlighter the words "Reality Check." I put it just out of sight so that I only tend to notice it every now and then. Every time it catches my eye, I do a check. Conditioning yourself like this can do wonders.