I've done some hiring. I'll chime in to say that too much prep is worse than no prep. The over gouged candidates sound like they are bored and insincere. If you've never had a legacy interview, get some coaching (EC or Cage, but not both, and beware, they are polar opposites in how they coach). Once you've done that for one, you should know what to expect. Just answer the questions honestly and sincerely.