If there is someone in a group you want to know more of, start by trying to make eye contact. When it is reciprocated, hold the gaze and add a smile. Arching eyebrows, winking, blinking and rapid eye movement, toying with your hair---all of these will let the other person know that you want to know her up close and personal. Some proactive flirts might do something more as well, such as lick their lips, touch the teeth or lips with their tongue, or puff their chest or breast forward. An open-legged stance or merely mirroring or copying the other person's posture are some other ways of conveying your message with your body. If you are already in a conversation with the person, lean inward as often as you can and pay attention to what she has to say. This will invoke reverse interest in you, taking you closer to your final goal.
When in a physically close position with your object of desire, try to gauge his vibe and touch him as often as you can without overdoing it. Play with his hands, touch his arm and try to keep eye contact though you might be, out of shyness, inclined to do otherwise. You will be prone to fidgeting and shifting your weight back and forth between your legs. Though these are signs indicative of your interest in the person, try to remain calm and smart and feel confident. Laughing at his jokes, whispering to him to instill a feeling of personal conversation and asking direct but polite personal questions about his status in life will go a long way in establishing your interest.
Always be polite, show adequate respect, and try to converse and act with discretion. Campy cheap pickup lines, vulgarities, improper touching or tactless conversation should be avoided at all costs. Make sure not to intimidate the person with your banter or behavior. If you are in a group and catch an attractive person's eye outside the group, give yourself a breather and take a break. This will provide the chance for you and the other person to connect away from the group. Nobody wants a rejection in front of other people. But if you find someone whom you do not like flirting with you, be polite but firm in your rejection. Do not lead any one on without reason.