You will need
  • - flowers
  • - postcards in the form of hearts.
Find out the girl, what she expects from friendship with you. No need to ask about it directly. Try talking with her to bring her to this answer, find out what are her goals for the near future. Maybe she already wants a more serious relationship, but waiting for your suggestions. But even if you feel that she doesn't want no relationship, don't stop there. Perhaps a story will help to change her opinion, and she wants to meet with you.
Prepare for this event. Many couples begin Dating without formal proposals, but if you don't want to miss out on the girl that you like, better to do it officially, and not wait until someone will do it for you. Think about the words you say to her. Will not really look good if you start to falter and show their uncertainty.
Organize a romantic date. It should not look like your usual walk. Ask friends for help. You can just go with the girl to the Park to walk and talk as usual. You will fall towards your friends who have silently handing her a paper heart with one word. For example, at the heart of every one word sentence, "Marina, be my girl." When all the hearts are in her hands, gave her a bouquet of flowers.
Admit to her his feelings. If you bring friends, there is no possibility or you want to be alone at a time like this, prepare a romantic candlelit dinner. This is hardly very original, but you can add unusual elements. For example, to pick up for the solemn moment was the right song to ask a girl to dance. The lyrics say it all for you, but you will not be silent. Give her a symbolic gift for two. It may be just a token denoting your feelings.
Be confident, don't hesitate to talk about what you feel for the girl. Your confidence can also play a role. Do not think that you will get a negative response. Most importantly, do everything from the heart, and then the girl will appreciate your action and accept you become even closer.