OK, so this question isn't specific to photographers. In fact, it can be applied to pretty much any business-related situation throughout your life. Anyone who hems and haws about giving out her cell phone number or e-mail address, or who makes light of other clients' "silly emergencies" might not take your concerns seriously, either.
Ask your photog candidate how long you can expect to wait for a reply to your questions. If you're a typical bride, anything longer than one business day just isn't going to appeal to your organizational sensibilities. Whatever you do, honor your instincts and run for the hills if she strikes you the wrong way at your initial meeting. First impressions tend to be pretty accurate, so if you find her to be annoying, elusive or noncommittal, chances are good that the same qualities will trouble you throughout your working relationship.