"Look" and "appear" are describing a physical condition. "seem" is an overall impression which could be based on other things in addition to a physical state. But in many cases it's a question of idiom as to which one we will choose. Try noticing where they are used in texts that you read or in songs, movies and you will see the slight differences.

There's a slight difference in meaning. I couldn't explain it myself, so I found a website that does a really good job at explaining it. 1:You should use look or appear "when describing an observable condition." EX: He looks angry/He appears angry. (His face is red and muscles are tensed up. Everyone can observe these features to see he looks angry) 2: You should use seem "to describe a perceived condition." EX: He seems upset. (I personally have a reason to think he is upset, but it may be only my perception, and other people may not think he seems upset) So in summary: Look/appear is more objective/everyone can understand Seem is more subjective/personally understand http://english.stackexchange.com/questions/21758/seem-appear-look-how-to-differentiate