There is so much second-hand information out there about the publishing industry. Instead of reading about something someone heard someone say, read it from the source. Here are a few great blogs to follow if you're actively querying or will be querying in the near future.
1. Pub Rants A Very Nice Literary Agent Indulges in Polite Rants About Queries, Writers, and the Publishing Industry. Nelson Literary Agency, LLC
2. Query tips straight from the slush pile readers. Speilburg Literary Agency