How do I find an agent for a 12 year old female actress who is just a beginner?
If you live in New York or LA, you can get a copy of Call Sheet and circle acting agents that represent kids, then mail a headshot and resume of your child to these agents.
The best thing, though, if your daughter is just starting out, is to start with a good child acting class. Not only will teachers be able to recommend good agents, but schools often organize showcases where agents can meet your child.
You can read more on kids talent agencies here.