It's good to have some statements prepared in advance that you know others your age, especially those you want to approach for friendship, like to talk about. For instance, watch popular TV shows and go to the movies. A good opening line is something like, "I just saw ### movie and it was great; have you seen it yet?" The same is true for music and, to a lesser extent, books. Still, being able to discuss them makes you interesting to others. See movies and are still not sure what to say? Read the reviews in the newspapers - they will often cover the relevant details and help you to feel comfortable about what you're discussing.

Also, sometimes is not so much what you say as how you say it. Smile. Make eye contact with the person you're talking to. Avoid negative comments, e.g., putting others down. Set goals for yourself, e.g., to talk to one person, to make one good friend who has common interests, to go out on a date, etc.

Good luck!