Dear Sarah,
 
The answer to your question varies very much from individual to individual. Some visit just one community, have the sense that this is home, and dont look any further because the more they get to know the community and the community gets to know them, the more obvious it is that this is where she should try first. There are others who reason their way into a particular group they really feel called to a particular apostolate or mission, they know they need a strong community life, etc and they search.

The common element seems to be the click, the impression somehow that you have found your home, what you were made for.  However, this has to be tested. There is a process of application, postulancy, novitiate, temporary vows, which are all stages in which the call is tested and proven more and more deeply. You are really only sure when you have gone through it all.

God bless.