Stay relaxed at all times, take a deep breath and do not panic with the nerves when staring near a girl that you like. If you see that she is clearly interested in you, after a few moments of non-verbal language, it is time to approach to her.
Keep the eye contact with her while you do not do something stupid like tripping over something. Stay safe and confident. Even if you stumble, do it as something funny happened and make her laugh.
Once you get her smile, approach and ask something like “it seems crowed this place, it cost me to find you between all these people” Try to continue the conversation, try to be pleasant and improve. It is your moment to progress with her, because she laughed about your clumsy moment, and in the most situations like this, you have won the first step to maintain a conversation with her.
If you are not good at talking to girls, it will be very difficult to seduce them, but never mind. Keep trying and you will soon learn get along with women conversation.