Present
Your presence must be noticeable. Walk tall, stand proud. She took the time to spend it with you. Time is the most precious gift one can give another. Appreciate her company, don't be absentminded.
Really listen
Show genuine interest and listen - the effort must be noticeable. When talking to someone, show some genuine interest in them - don't just use them for stress relief or as a witness to your accomplishments or an audience to explain your latest fascinations to.
Listen to them when they are telling you something about themselves. Don't just nod while listening halfheartedly. Really listen - and then show some interest, ask a question. And then remember the answer.
Be observant and be curious - you should find out what she likes in detail - then you will have no problem deciding what to buy her for her birthday or where to take her on a vacation.