Real Muslims live the principles of Islam instead of talking about them. Just like a real anything, poet, philosopher, warrior, etc. is known by the way they ARE. You'll know a real Muslim when you talk to one simply by his or her disposition. They sacrifice sleep for the early morning prayer. They fast, even when it's not the Holy Month of Ramadan. They control their speech and emotions. Even in the face of the ignorant, you'll see an air of calm and precision in their manner. Picture every other personification of control and strength, Samurai, Shaolin Monk, whatever, then add, instead of Bushido or Buddhism, Islamic principles and you have what you refer to as a real Muslim.