Best Way to Create Multiple Partitions on Macbook Air 13" 2012 solid state drive (256GB)

I just bought a Macbook Air 13" 2012 solid state drive (256GB) w/ 8GB Ram and I would like to be able to dual boot to Windows 7 and have a 3rd partition to share files between both Operating Systems. Can someone point me in the right direction, recommend partition sizes, pros and cons etc.? Should i bother with the 3rd partition or just by an external HD?

FYI,I will mainly be using the MBA for programming in Visual Studio 2010 and some ios development. Thanks in advance.