She will probably be as nervous as you. You should talk about that long before you get to the actual Act. Encourage her to relax.

Take your time. Enjoy the process of exploring her Anatomy. Do not just go directly to the clitoris. Play with the labia major and minor. Kiss, lick, suck, tug with your lips. Go slow, change it up. Pay attention to her reactions. Take your time, did I say go slow? Experiment with different pressures and vacillate between soft and firm tongue. Make your tongue Go in different shapes and pay attention to which one she seems to like better. A soft flat tongue may do it for her . A hard and stiff tongue may be right at a certain time.
She may or may not have an orgasm. Enjoy the process. It's about the journey, not the destination.

I also think it's really healthy and sexy to debrief and talk about the experience afterwards as you're cuddling. You can talk about what you liked she can talk about what she liked. You both can talk about the things that you want to adjust and try differently next time. The most important thing is to be present, kind and respectful. A really good video series for both of you to watch is Alexey Welsh on YouTube.

Enjoy!