A friend is someone you respect, have fun with and share values with, says relationship coach Denise LaFrance in "The Friendship Foundation & Why It's So Important," an article published on the website YourTango. Two people who have invested more time building a strong friendship are more likely to stay together than those for whom sexual attraction is the top priority, LaFrance says. Knowing how to recognize the promise a friendship holds and nurture it toward romance can help you change a friend into a boyfriend.

If you are thinking about the possibility of becoming a couple, perhaps your friend is too. Pay attention to his behavior around you. He may appear nervous or preoccupied. Observe his body language as well as what he says. He may look for opportunities to make physical contact with you, such as linking his arm in yours as you walk through a park, or "accidentally" brushing his fingers against yours as he hands you a cup of coffee. Be aware of his eye contact. If he is interested in you as more than a friend, he may hold your gaze for a few seconds longer than is necessary. "The flick," a more overt sign of sexual attraction, reveals body language expert Judi James in an article titled "Language of Love" for "The Guardian." This is when someone breaks eye contact to look at your mouth, before looking back into your eyes.

Dropping some subtle hints will help you determine how your friend will react to your suggestion that he become your boyfriend. When discussing your plans for the weekend, suggest you do something that you wouldn't normally do together, such as watching a movie -- an activity that's more "date" territory. If you tend to see each other in larger groups, ask him to meet you on your own. Start a conversation about dating and relationships, and ask him what he's looking for in a partner. Tell him that you think the best relationships start with friendship. Be a little more playful in your manner. Some lighthearted teasing will help to take your relationship to the next level. For example, if he has a new hairstyle, say something like, "Wow, that's a little short. Don't worry, you're still cute!"

If you want your friend to see you as girlfriend, you need to make him see you as the best potential girlfriend ever. Make even more of an effort than you normally would to make him feel special and valued. Support him in everything he does, and compliment him regularly. The right compliment will help to strengthen your bond, says Hara Estroff Romano, editor at large of "Psychology Today," in the article "The Art of the Compliment." Tell your friend how he enhances your life -- for example, "You make me feel more confident to pursue my goals" or "I love the way you make me laugh." Show him you are thinking about your relationship on a deeper level and he may start doing the same.

If you're absolutely sure you want to turn your friendship into romance and feel fairly confident that your friend will react positively to the idea, it's time to summon up the courage to ask him out. You'll need to make it clear that you are asking him out on a date and not just to hang out as friends. For example, say something like, "I feel a little embarrassed asking you this, but I think you're great. Would you like to be my date to a party this weekend?"