The cute (and oh so true) answer is, if it's in your house it's already dominated you. Question moot.
The biological answers are also pretty straightforward. Direct eye contact, particularly with slitted pupils, is often a direct challenge and an open invitation to fight. Ears flat, or canted backwards, can also be a sign of aggression, as can a tail standing straight up and lashing in short, sharp arcs. A cat who's trying to dominate you physically will often make quick dancing steps toward you, turned slightly sideways to appear bigger, in an effort to frighten you away. And the ultimate aggression is a growling bite, not short nips of fear but a claw-grappling, back-leg-kicking, deep chomp designed to immobilize rather than drive away the opponent. These bites are pretty rare and are driven by a very different stimulus than the typical "fear bite" (pounce, bite, retreat).
Mental domination in cats is much more subtle and is generally a war of attrition. Cat wants food on counter. You don't want cat on counter. Cat gets on counter anyway. Eats food. You booby-trap counter. Cat demolishes booby-traps. Cat eats food. Rinse and repeat. Eventually, you stop leaving anything edible or breakable on counter and cat now owns counter for play, napping, and surveillance.
Understanding a cat's body language, and knowing how little cat-minds work, is a huge part of successful cat ownership. They are stubborn, independent, intelligent creatures who are quite capable of forming intensely loving bonds with their people, but on THEIR terms, not ours. They're not eager to please like dogs, they don't have a pack mentality, and they demand respect and reciprocity from their human companions in ways dogs don't. Consistency, calm responses, and a sense of humor are all necessary to enjoy a cat to the fullest. When we come to love them for who and what they are, rather than expecting them to be slavishly devoted to us, then mutual respect can lead to a very rewarding and satisfying relationship for years to come.
Read what your cat is telling you with his or her body, particularly eyes ears and tail. Chances are, good or bad, he or she MEANS it. Whatever else they may be, cats aren't liars. If a cat is showing signs of dominance aggression, the habit must be broken QUICKLY and DECISIVELY before it's too late. A dominant cat running the people in a household is a sure recipe for disaster. No one is going to be happy.