There's a few little things that let you know someone's thinking about you:
1.They send you a good morning/good night text almost every night
2.You catch them staring in your direction a lot
3.They try to look at you when they think you’re not looking
4.They talk to their friends about you or randomly bring your name up (doesn't have to be all the time)
5.When they bring up things you said in your past conversations
6.They subconsciously wander in your direction or walk close to you