As an ardent student in the school of Ian Kerner, I feel I cannot emphasize enough the importance of coreplay. The very focus of this thread (intercourse) illustrates a very phallocentric method of approaching women's sexual pleasure - and one that is off kilter.
Realize that all three of the largest sex studies of the 20th century (Kinsey, Masters & Johnson, and Shere Hite) all found that less than 30% of women are even capable of reaching orgasm through intercourse. Sex therapists (except perhaps those stuck in the sick world of Freud) now agree that intercourse is only fourth on the list of best ways for a woman to reach orgasm - with masturbation, oral stimulation, and manual stimulation all besting it.
Thus, it is a rather poor idea to have the predominance of sexual activity occur during intercourse. It makes much more sense to make an activity like oral sex, which is a much more reliable means to the end of orgasm, the core focus of sex play. On top of your traditional foreplay, add 20, 30, 40 minutes of oral sex. No you don't have to lick her like a porn star for that long (in fact please don't, most women will tell you that doesn't do much for them).
Lavish affection on her thusly, and she is sure to reward you in kind.
I would very much recommend purchasing Ian Kerner's She Comes First: The Thinking Man's Guide to Pleasuring a Woman, if only for the multitude of references to the legendary Strunk & White of English composition fame.