First and foremost, I personally think you need to learn about Windows Presentation Foundation and grab the concepts from it as those concepts are brought forward to Silverlight. Learn about XAML and how and why its used. Silverlight is something you can pick up on the go as you'll be using it with XAML. These will make it easier to actually quickstart (live login required) your Windows Phone 7 development. You need to pick up on events, delegates, and other little C# things to be able to effectively program and understand your Windows Phone 7 app. Events are pretty easy to pick up on as you'll be using them on a daily basis throughout all applications nowadays. Delegates are C# function pointers. As a result, you can use anonymous delegates to create throwaway functions on the spot. If you want to move into XNA for Win Phone, sorry I'm not up to that yet! Someday, I will though.
Importantly, once you start don't stop. Obviously you can stop reading/programming for the day, but don't give up quickly.
What resources do I recommend? Look at the MIX videos as they provide insight and inspiration for developing Windows Phone 7 Apps. Go to MSDN, for help with programming and getting started. Here is 30+ Excellent Windows Phone 7 development tutorials for different things you can do. There's many more, so Bing them!
(Skip, if too long!) I thought I should tell you that developing the UI for Windows Phone 7 is no easy task. It really takes getting used to because of its innovative interface. It is not like creating an Android or iPhone interface where you can go tabs/buttons free! It can be frustrating to see your test application isn't coming well because it doesn't feel right, but that's fine. Its apart of the learning process, finding out what works and what doesn't. What doesn't work is usually engrained in the brain as to avoid doing it again. Also, just because something doesn't work in your eyes doesn't mean you can't get opinions on whatever you are trying to do. People can help you see different ways as we developers are usually accustomed to our ways of looking at UI based on our experiences.
Microsoft has a free book for you readers out there! Programming Windows Phone 7!