I think the first thing is to look at the girl. If she is a very attractive girl. She likely gets a lot of validation. If she is actively seeking validation, then I know validation can be a huge tool. There are girls who seek validation rather explicitly within minutes of meeting them. I know a huge validation strip will not scare her away but make her more active. More invested. More attracted even.
If you're gaming a 3 and you're negging and trying to strip validation... well it's not going to work. She likely needs to be given validation rather than stripped.
How do I determine in which way? Sometimes I don't. Sometimes I'll go through subtle validation strips until she is reacting to one of them.