tl:dr: I'll move according to the situation.
If he's taller then me, I'll go for the hit-and-run. Shorter, then I play the range card. If he tries to go for the killing blow right off the bat, I rush in and kick him in the solar plexus with a good side kick. If he's smart, I'll play defense game until he's open. If he has a weapon, I try to remove it. If he tries an over-reaching strike with a bat or similar blunt object, I close in to spot where, if I get hit, I'm not taking much damage. If he has a knife and he's holding it conventionally(blade extending from the thumb), I wait for the lunge and take control of his arm. If he's holding it slasher's grip, I'll use something that beats his range of his knife (slasher's grip reduces knife range, and most people will rely on the knife if they have one). If he is primarily a grappler, I'm going to to keep the range short. I have terrible balance and overextending would be dangerous. If he primarily uses punches, I'll aim for the legs with a low kick. If he starts with a high kick, I'll sweep. If he starts with a mid-level kick, I'll grab his leg and throw him down. If he starts with a low kick, I'll play defensive until he slips up. If I know he's a better fighter, I'll either a) run away b) fight dirty, like a tiger in a cage (if he does martial arts as a sport) c) hide behind the women (only if a and b aren't good options). I'm very small and very young looking so it's an option, so don't judge me.