That my friend is the best way to go. Unfortunately Microsoft has yet to see it that way...so you must use a third party boot manager to achieve it.

I use BootIt NG from terabyte as mine for multibooting configurations. It runs about $40 (US) A free version is GAG.
GAG does the same but limits itself to only 9 different installations. I have tested it and it is a great free program.You will need to Google for it though!

For a quick explanation...the installed boot manager in windows and windows itself limits the botable partitions to only 4 so if you need more you will need to do all your partitioning with the 3rd party boot manager. Most all work the same.....

The program installs on the pre-configured 8mb of lead in space that is before every partition that is created. Once installed it sets up a pre-boot screen that allows you to choose which operating system you want to boot to...which can be auto configured with a specific time limit to change this. Once the operating system to boot to is selected then all other master boot records are hidden to protect the integrity of each operating system....this allows you to share folders and files (not applications or programs) between the different operating systems...

A nice clean simple installation of each operating system is all that is required so no special boot configurations or anything like that is needed....

note....not all operating systems can see the same file systems so conciderations concerning that in file sharing is needed...for instance...XP installed on NTFS can read W98 installed on FAT32 but W98 cannot read the XP files unless XP is installed on FAT system as well.

To start... two ways
1) more than 4 operating systems you need to install the boot manager program prior to any partitioning....then use it to partition the drive or drives. Then install the operating systems in any order making sure that each operating system is fully updated and applications will have to be installed to each system.
2) for less than 4 operating systems then install the drive with the operating system already installed and just install the new boot manager and it will install itself and prepare for other installations of the operating systems.

I do this with all my beta programs...that way if there is a problem I don't screw up the other systems.

edit:
Each operating system will have to have its own license or activation code. Also the same with anti virus and anti malware programs and they will need to be configured to only be used on the partition that it is installed on or there can be conflicting false positives.