Make eye contact -- the more, the better.
Prolonged eye contact shows your potential mate that you're interested in what she's saying, and that you want to get to know her on a deeper, more intimate level. Eye contact is also easy to initiate with a total stranger from across a room, so it's convenient to use in almost any situation.
Break the personal barrier.
Humans have subconscious barriers set up for different relationships. Personal space, which is reserved for friends, is the space within a 3-foot radius of yourself. Intimate space is within 1 1/2 feet. Get closer as you flirt to indicate that you're moving from stranger to a more intimate encounter. Take the hint if your partner moves away from you as you approach him though. Part of subtle means receiving signals, as well as sending them.
Mirror your partner's posture.
Pay attention to her gestures and posture in particular. If she's leaning on the bar, do the same. This is a very subtle way of flirting, and your partner might not even be consciously aware of what you're doing. But according to the Social Issues Research Center, experiments have proven that when someone mirrors his partner when flirting, he gets a higher rating than those who don't.
Touch your partner in an appropriate way.
While groping is never appropriate (or subtle for that matter), a simple touch can be an intimate signal that you're interested. A brush of the shoulder while laughing at a joke, for instance, can be a powerful indicator that you like your partner, without being so obvious as to be considered needy or desperate. If, however, your partner shows disinterest from even the most subtle and appropriate of touches, then she's probably not interested.
Smile, laugh and nod.
These are all little indicators that you're having a good time, that you like your partner and that you're interested in what he's saying. It's also important that you be genuine however, as fake smiles can be a turn-off, and the wrong kind of nod can stop the flow of a conversation. One or two short, quick nods are best when listening to your partner speak. Avoid long, slow nods or too many quick nods as these can kill your partner's train of though, thus killing the conversation.
- Take the hint. If your partner seems uninterested, move on and forget about it. Everyone has different tastes, and just because you don't appeal to one person, doesn't mean that you won't appeal to someone else.