Supreme Court Nominee

OK, we just discover that the FEMA director had no real experience with handling emergencies. Everyone is up in arms about it. Now we get a Nominee to the Supreme Court who has never been a judge. How does this work? Harriet Miers may be a good attorney but she has no experience as a Judge. Even Judge Judy has more background for this nomination. What kind of attorney was she? Most specialize in one area or another, IE criminal law, contract law, etc.
Does she have the necessary diversity that will be required of a Supreme Court Judge? Does she know Constitutional Law like the back of her hand? I applauded Bush for his nomination of Chief Justice Roberts. This man knew his law and seemed to have a broad background. I can't do that for his latest nomination. It seems like typical "good old boy" (or girl in this case) politics.