Whatever you're doing at the time. According to a survey by the Association for Research Inc. (cited in The Book of Sex Lists, by Albert B. Gerber, first published in 1981), the ten sexual activities preferred by heterosexual women (in order of preference) are:

• Gentle cunnilingus (on the clitoris) by a man
• Gentle finger stimulation of the clitoris by a man
• Sexual intercourse on top of a man
• Sexual intercourse in a variety of changing positions
• Receiving cunnilingus (gentle, of course) while performing fellatio
• Massaging a man all over
• Masturbating a man
• Being petted, kissed and stimulated manually by two men, culminating in intercourse with one man while the other alternates between gently stroking the clitoris and nipples
• Masturbation
• Performing simple fellatio

• Fellatio by a woman to orgasm
• Intercourse with a woman in a variety of positions, changing from time to time
• Nude encounters with two women in a variety of activities, changing from time to time
• Petting the breasts of a woman
• Anal intercourse with a woman
• Performing cunnilingus while the woman is performing fellatio
• Performing (consensual) mild sadomasochistic acts upon a woman
• Being masturbated by a woman
• Performing simple cunnilingus
• Masturbation