There is a free online course available on Microsoft's Virtual Academy to prepare you for the exam. Even better, Microsoft are giving away a free exam voucher, as long as you take it before 30th June 2014.
Even though I don't currently use Server 2012 or System Center, this was too good an offer to turn down and an opportunity to learn about these technologies for future reference.
The MVA videos were really good, however I personally don't think that these alone are enough to get you through the exam. I checked out the official list of 'Skills Measured' for the 74-409 exam, researched each topic in turn and made notes. This worked well for me. Whilst researching, I came across useful blogs, articles and videos by John Savill, Keith Mayer and Aidan Finn, so a mention needs to go out to them.
In reflection, I have come away knowing a lot more about Hyper-V and System Center 2012. However my opinion is you can't just pass the exam then expect/be expected to build complex datacentres, with multiple logical networks with tenants that require isolation etc etc! This would need to come from experience or further design/architecture courses.
If you are planning on taking this exam, good luck.