That’s a hard question. Different ppl have different ways of expressing themselves so you just have to look for signals you think that person would give you according to their personality. If it’s someone outgoing and talkative it’s probably very easy to know because they’ll text and talk to you a lot and make excuses to be with you or compliment you a lot. If it’s someone shy sometimes you can catch the person looking at you when you’re not paying attention or trying to talk to you and getting nervous or idk stuff like that. This is very subjective cause sometimes even talkative ppl aren’t good at expressing themselves when it comes to love so… yeah… Either way, if you’ve known the person for a while and see/talk to them regularly I think you’ll know, like, you’ll feel that there’s something there. The vibe is different around ppl that like you 💕