I don't read them, I let them speak :)

I can't read people except they write letters on their forehead wkwkwk :p

Sri lestari can't read people coz she cannot stop giggling long enough to actually focus on them wkwkwkwkwk!

Body language, actions, and eyes. 

You could make this into a science if you want, here are some simple signs:

Look at their body. How are they carying themselves?

Do they make themselves smaller, curling up? - they are uncomfortable and shy, afraid,....

Crossed arms? - Blocking you out, defensive, reating instead of acting

Leaning towards you? - agressive, attacking

Do they take in a lot of space, expanding themselves, showing armpits? - Dominant, confident, calm, relaxed, self assured, happy, satisfied

Tight jaws - agressive, anger

tense forehead - unsatisfied, troubled, anger

neck dropped foreward, chin dropped - ego-centric, uninterested, closed minded

Basicly any contraction is negative feelings, attitude,...

And any expansion is possitive. Both in face and in body. Also the eyes tell you a lot. Look into peoples eyes and just trust your instincts. By consiously changing your own body language, thus 'faking' to be happy,.... by expanding yourself, is proven to actualy really make you more happy and confident.