> #define CTL_CODE( DeviceType, Function, Method, Access ) 
> (                 \
>    ((DeviceType) << 16) | ((Access) << 14) | ((Function) << 2) | (Method) 
> \

This cryptic #define makes 32 bits constants as follows:

dddd dddd dddd dddd aaff ffff ffff ffmm

Legend:
d: DeviceType
a: Access
f: Function
m: Method

You can construct the constant in this simpler way:

CTL_CODE = DeviceType * 65536 + Function * 4 + Method + Access * 16384


> #define IOCTL_STORAGE_GET_MEDIA_SERIAL_NUMBER CTL_CODE(IOCTL_STORAGE_BASE, 
> 0x0304, METHOD_BUFFERED, FILE_ANY_ACCESS)

In the above, we have these constants:

IOCTL_STORAGE_BASE = 0x0000002d, or 45 decimal
METHOD_BUFFERED = 0
FILE_ANY_ACCESS = 0

So, IOCTL_STORAGE_GET_MEDIA_SERIAL_NUMBER would be:

CTL_CODE = DeviceType * 65536 + Function * 4 + Method + Access * 16384
= 45 * 65536 + 0x0304 * 4 + 0 + 0 * 16384
= 45 * 65536 + 772 * 4
= 2952208, or 0x002D0C10

> In the above example, how was the value of parameter 0x2D1400 determined?

See the bits distribution above. When 0x002D1400 is broken down, you get:

DeviceType = 0x002D
Access = 0
Function = 0x1400 / 4 = 0x500 or 1280 decimal
Method = 0

I couldn't find any constant for 0x500, so it's either for later versions of 
Windows, or undocumented.