It's in his eyes
if you tell him a story and he's actually interested, if he helps you solve problems in your life, if he says, 'i really care about you':P
Pretty obvious if you look close enough. He spends most of HIS time with you when he could be doing other things. If he visibly tries hard to get your attention, impress you, tell jokes... Basically anything that translates into "HEY YOU! LOOK AT ME! I LIKE YOU!"
And after he gets your attention, he likes to talk about you and get to know you too
sometimes their emotions won't show but there eyes will show there emotions towards you. they will give you a look and you will know. and specially if they ant embarrassed of you some guys don't want anyone to know they is dating you.
If he is consistently good to you... wants to be with you...does things for you..etc. Ignore what we say unless we show we can prove our words with action. If he really cares about you...he will do anything for you without expecting ANYTHING in return.