Originally Posted by
Merlock
A dream sign is a sign that signifies that what's going on is a dream. Something out of place, something that doesn't make sense, etc.
A reality check is an action you take up to check whether you are dreaming or not. The idea behind reality checks is to make them a habit.
So combine both. Be aware when awake, and do reality checks both whenever they come to mind and whenever you see something out of place, something odd, something that grabs your attention all of a sudden.