Do Damage Control as Soon as Possible
This is key. Ideally you didn’t make your move until after taking time to fully check her or her profile out. If you did so, you’ll have plenty of time to read the cues that something is wrong, maybe she frowned or averted her eyes. If you find you’re not getting the response you wanted, you can still salvage the situation. Steer the conversation quickly to a neutral topic. Even the news or the weather will do. This gives you time to replay the conversation in your head and identify what might have rubbed her the wrong way. Maybe you came on too strong when you complimented her. You want to move a little more slowly if you’re trying to pick her up outside usual hook up spots like bars and clubs. Chat her up a little first before telling her you admire her looks.
If the exchange took place through email or IM, perhaps her replies changed in response to something you said, perhaps she stopped replying at all. Some women find it hard to be direct and tell you that they’re no longer interested. Fixing things is harder if you’re talking to this girl by IM or email since you can explain or backtrack as much as you like, but if she just deletes your reply, there’s nothing you can do about it.
When It’s Not What You Said
Perhaps it wasn’t what you said, but your manner or even how you looked or what you were wearing. For example, if you realize suddenly that you just asked a woman for her number while wearing ripped jeans and an old T-shirt with holes and grease stains, shame on you. It might be that you’re just running to the car parts store on a lazy weekend. But she has no way to know that unless you tell her. Be honest and give her the context as casually as you can. You don’t have to make a big deal about it, and don’t act overeager. Just don’t leave her with the impression that you’re a homeless hobo.
Don’t Give up, Even If “Soon as Possible” has Already Come and Gone
So, let’s say you’re reading this post days or even weeks after making that bad impression. You’re no longer in the moment and many of the above options no longer apply to you. If this is the case, you should still try to get back in contact with her as soon as possible, depending on how bad your screw up was. One thing you don’t want to do is let so much time pass that she forgets whatever good qualities about you she did like.