Sex starts well before the first article of clothing hits the floor. The real foreplay is appreciating her on a daily basis. Making her feel special, and sexy, and enduring her boring work stories without so much as a complaint. It begins when you touch her back at a party, or exchange a knowing look across the room. And yes, by occasionally sending her suggestive text messages about what you'd like to do later.
All of this ensures that when you finally get time together, she'll want to tear your clothes off before the door closes. You're hers and she's yours, and nothing could be hotter.