And before anyone gets any stupid ideas and reads this as if deep penetration is the way to go, or stimulating either fornix leads to earth shattering orgasms, please understand that each woman is different (many no longer have a cervix or uterus and that is okay - nature did not design us 100% perfect). You need to work out what works for your lady in particular. My wife likes deeper strokes, but it can also lead to pain and overall she is far more likely to get off on clitoral stimulation or fingering of the first few inches of her vagina. Regardless of what or how is physically stimulated, your best bet to getting her to have an amazing experience is to get her in the right state of mind. Find out what her kinks are, be a gentleman in general, go the extra mile, learn her body, ask for feedback, and she will be be having an amazing time if you get much of it right and work on her brain as much as on her body.