What oder do you put OS with a dual boot?

Answer 1

Depending on what you mean by order, and which OSen you're putting on the machine.

If you mean, in which order do you install the OS, it's generally a good idea to install Windows first, and then Linux, as Microsoft doesn't even attempt to give their boot facilities the capability of recognizing an operating system that isn't the current version of Windows or older, whereas virtually every Linux bootloader is given the capability to recognize non-Linux operating systems. Thus it's generally a good idea to install Linux last and allow its bootloader and not Windows' to be in control of system boot. This enables you to boot both Windows and Linux, whereas if you install Windows last, you won't even be able to tell Linux is even installed, let alone boot into it, without reinstalling the bootloader.

Keep in mind the above assumes a BIOS-based boot. The issue is less important to non-existant on UEFI, which was designed to allow firmware-level operating system boot order to be specified, assuming the implementation is correct. I personally use rEFInd on my laptop and have to shoehorn it into the Windows boot manager's place to get it to work properly.

If you mean "which operating system should be default" that is entirely a matter of preference. I personally make Linux my default. As it is I only ever use Windows for games, and at times I've been known to completely wipe Windows off my computers if I don't use it for a long time.