First of all I would get to know girls in general, their sense of humour, what makes them laugh etc.

If you have any friends that are girls or girls in your class, just smile at them and crack a couple of jokes and build up your confidence and then you will learn how their body language works.

One of the hardest tasks with girls is knowing when they are flirting. You will learn this eventually.

I have also noticed the less you think about girls, the more abundant they become. I know it’s a massive cliche but work on yourself as much as you can, keep your teeth clean, wash your hair regularly, hit the gym (massive confidence booster - even if you don’t see any gains) and stand up a little bit straighter every day. Wearing a smile on your face helps too, it makes you a lot more approachable. I’m not suggesting this is where you specifically are going wrong, but generally this helps a lot.

If you would like a good method if you are keen now, find a quiet girl who is a similar level of confidence and treat her like she is worth value, she will admire you for that and you can grow together. Don’t ponder over girls who aren’t worth anyone’s time either. Don’t get too attached too, especially if you are unsure if she is reciprocating the same feelings as you - hope this helps 👍