Make eye contact. A flirtatious gaze will certainly get his attention, even before you say a word. Eye contact plays a vital role in sexual attraction, according to Cheshire Therapy.com. If he glances your way and returns your gaze, then he might be interested, too.
Smile before you greet him. This lets him know you are interested. This is a strong signal for a female to send. It removes any doubt from a guy wondering whether or not you are into him.
Move in closer to him. Getting closer to the guy you're interested in signals that you're interested. Watch his body language to see how he is responding. If he is looking over and meeting your gaze, smiling and moving closer to you, then he is definitely interested.
Speak to him when you feel ready. A simple, "Hi, I'm Jane" is enough greeting to start a conversation. He will most likely return your greeting with enthusiasm if he's been showing signs of interest.
Focus on him and be involved in your conversation. Keep the conversation light and easy. Avoid heavy or controversial topics in the beginning.