There are many ways to tell someone you like them For instance, you should touch your hair or face while you are chatting with them. Do laugh whenever they tell you a joke.
Also, caress their knee or arm when you are having fun with them. At events like parties, keep an eye on their glass and fill it up when it gets empty.
Look at them clandestinely from the corner of your eyes at a distance in class or at party. Call them by their names when you are gossiping with them. Yes, people feel good when you say their name in front of them.
Hope this helped!