Most Helpful Guy
Simple small stuff. Body language mostly, If he/she gets nervous in front of you/near you. If he/she looks at you alot. If He tries to display dominance, this can mean quite a lot of things, its really easy to notice. If he talks about you /with you alot, Maybe he/she shared something private with you is also a big give away.
So yeah. Bodylanguage. Learn about it and just sneak-ish-ly find out if he/she is attracted to you. Its really easy to spot if you know what you're suppose to look for!
Hope it helps! :)