You really like somebody and want to impress the girl. Well, there's nothing wrong with that. It actually gives you a chance to make new friends and put your best foot forward. But then how to start. Well, here are ideas that can surely get you started.
Look Sharp

Everyone likes a sharply dressed man
The first and the foremost step to impress girls is to be formerly and properly dressed. Look sharp and neat, maintain your hygiene and be well groomed.
Be the center of attention

Friends, laugh, fun
Don’t be an introvert. Whenever your class starts or ends, talk with other classmates, surround yourself with friends. This way she will see you being the center of attention and will get curious about you.
Be helpful

It won’t hurt to be helpful
It’s nice to be helpful and not just to her, but to others as well. Because chances are she will hear about it through someone or she might see you and get impressed.
Treat everyone well

Be appreciative of others
If you want to impress girls, then you would need to treat others well. Be funny, but don’t be rude, be sarcastic, but know when you are hurting someone’s feelings. Because she’ll see how you treat others to estimate how you’ll treat her.
Remember to smile

Smile to the beginning of a friendship
Girls like men who are confident, but moreover, who are happy, friendly and welcoming. If you ever caught her gaze don’t look away as that is a sign of nervousness, just give her a little smile or a nod nothing big but yet subtle.
Watch your body language

The art of body language
Your body language can say a lot about you, even without you opening your mouth. Always maintain eye contact when you are talking to a girl and listen to her like your life depends on it. Also, avoid crossing your arms, as subconsciously it might seem like you are trying to block her.