The guidelines are split into 10 sections, and the overall guidelines seem like fairly common sense things starting with making sure your app meets the Core App Quality guidelines, and moving on to pretty reasonable ideas like making sure your layout, fonts, images, and widgets all are designed for use on larger screens, and that the app has all of the features of the phone version.
It's the last few points on the list where Google gets into more interesting ideas that aren't necessarily common sense, because they are common issues that may be overlooked. First, Google wants devs to stop requiring hardware features in tablet apps, specifically making sure that apps don't require telephony or cameras, because those are the most likely omissions from tablets (like say the Nexus 7). On the flip side, devs need to be better about declaring apps compatible with declaring screen support sizes, especially now that there are layouts for phones, 7" tablets, and 10" tablets. And, lastly devs should be taking advantage of the various options available in the Google Play Store like being able to have multiple APKs on a single listing that will dynamically be pushed out depending on the device of the user.