I always declare, and I always get sent to the ag screening. If you don't declare food products, you do run the risk of being fined ($10,000). I usually see the beagles working with ag agents and they are surprisingly good at sniffing out food products.

Here's a site that should help with your questions.

There's also a specific link at the bottom to answer your questions about meat. The short answer is most meat products are not allowed, and getting caught with them when you haven't declared them could be a painful experience.