I know this link isn't maybe the best of all possible resources but the USPS has a web area that does a pretty good job of explaining the new size & weight rates. If you go to:
There is a lot of information there. Several pages have some good descriptions and explainations of how to go about making sure you stay in the lower rate. Except it's pretty difficult to FOLD a 5 Foot Rake handle to fit into an envelope for a cheaper rate. LOL
Locally they are doing training classes at the main postal center but they are $250.00 per person. I don't think I'll be doing that any time soon. That's a LOT of postage.