As @Keysha says, variation is important. There is no standard Manual of Arms for cunnilingus, especially in the preparatory part. My lady liked a lot of “teasing” with lips, tongue and fingers starting actually quite far away from her genitalia.
As @Dr_Lawrence indicates, knowledge of the anatomy is crucial. If niether of you are sure (it’s possible!), there are several websites that offer tasteful diagrams and drawings to orient you to the “anatomy of Venus”. Diagrams are better than photographs, IMHO, since ladies anatomies vary somewhat and a well-labelled diagram is less confusing than a photograph.
As @Violet states, the tongue is your primary instrument. Lips and fingers come into play as your confidence and her desires direct. Violet is correct that your focus should be on her clitoris, but don’t head there immediately. She has to be ready for that first and that will be apparant when the clitoris emerges from her “sheath”, even then start gently. Think “nipple”.
When you begin to add fingering, remember that the G-spot location varies almost for each lady. Usually 2–3” in, alongside or surrounding the urethra. Stroking with one or two fingers, experiment with pressure and rhythm. Combining this with cunnilingus is something you have to learn to coordinate. Don’t forget what your tongue and lips are doing.
Anal play is another advanced area that some ladies love, some detest and others are so delicate that injury is a real possibility. Only approach this with great caution, and NEVER introduce anything that has been placed in her anus into her vagina unless it has been sterilized first (including and especially your fingers and sex organ). Infections are nasty.
It may seem to take away from spontaneity, but discussion beforehand can prevent much disappointment. Once you both know the basics, then you can experiment and add “spices” to the experience; bondage, little nips with the teeth, toys, etc.
Use all your senses; aroma, taste, feel, appearance and most especially your hearing. Listen to what she is telling you, not only in words but breathing patterns, moans, purrs, etc. What you ate for dinner, time of the month and state of arousal will vastly affect taste and aroma; think of the experience as a feast, each session as a new course to be experienced and savored.