Pick up the phone, and give them a ring. Surprise them, and talk in a sexy voice.
For many of us, it's been ages since we talk on the phone like we did when we were dating. Now you live together, and in the instance that you're not together, when one is at work, the average conversation has something to do with "Honey, could you pick up ____ before you come home?" Or, "What do you mean that bill didn't get paid!"
While normal, everyday conversations are great, and are essential to keeping the lines of communication open, throwing in a sexy conversation every once, and a while will help to keep the romance alive.
Surprise your partner, by simply calling to say something sweet, or sexy.