If I have some decent sources, like census records, or birth or death records of children, then I make a guess at the birth date based on those. If I do not know the LNAB, then I don't create the profile yet, just talk about her in her husband and children's profiles. If I've done exhaustive research, then I may add her as an unknown, but I really hate doing that, so normally don't. I also guess the location, especially if the husband and children were from the same place. For the US, it could just be the state.