Polish your vocabulary: One of the greatest difficulties couples have when it comes to sexual communication is an inadequate sexual vocabulary. Some of us may never have had anything more than locker-room talk to discuss sex. Start by learning the proper words for body parts. This might seem too clinical at first, but it offers a way to talk about sex when you're not having sex without offending anyone with slang.
Ease in with texting: Try sending your partner a text that lets them know something about your sexual preferences. For example, say, "When you do ____, it gets me in the mood for sex." By doing this, not only will you get them excited to see you later, but you'll also be practicing sexual communication and letting them know what you like.
Use the phone: If texting just isn't your thing, try using the phone to talk to your partner about sex. Randomly call and communicate what your favorite sexual position is and why. This doesn't have to turn into phone sex -- in fact, it shouldn't. If you're shy, call your partner and tell her that you had a really sexy dream about her and describe what you want in very sexy terms as though it was part of the dream.
Practice with each other: This might be a little bit awkward the first time you do it, but it's worth it. Sit down and practice using your newfound vocabulary with your partner. Talk about sex outside of the bedroom, in a non-sexual setting, and practice getting comfortable using sexual communication as a way to converse. You can still make the sex talk sexy by expressing your desires in positive sexy terms.
Research shows that couples that can communicate openly about sex are more sexually satisfied. This has also been shown to impact their overall relationship satisfaction, with couples that successfully communicate about sex showing higher levels of satisfaction than those who don't.