I'm shooting from the hip on this one, since I have no idea which standard is driving you to have to do this. I can only write from an ISO 17025 standpoint, which states that all locally developed methods must be validated.
The key word in this is 'method'. ISO makes quite a distinction between 'method' and 'procedure' in that you can write a local procedure based on recognized methods.
For instance, since you are known as TorqueGuy, I'll write an example on that. I write a nifty little procedure on calibrating a torque wrench that fits how I do it. I place the bar at the midpoint of the handle, apply pressure, the transducer display beeps, gives me a handy MAX reading, and I write it down. I may have written the procedure, but I most definitely did NOT develop the method, as it is the method you will see published in numerous accepted standards and specifications. Standard methods are validated long before you or I learn them, and I don't have to validate them, I just have to develop my uncertainty budget.
So, in short, if you are in an ISO 17025 setting, it is very likely that your method does not need to be validated, unless you are doing something that no one else has ever thought of and documented, which is quite rare. If it is a QS company that you are with, I have to defer to the experts here.
I'd leave you a nice email address to contact me directly, but it seems that I have resigned my position where I work and I am moving on to more coastal pastures, so my email addresses will die in the next week or so.
Ryan