When adding parameters to a project they are put in the properties in the order they are put into the project.

Thanks, logical and known.
Not exactly what i'm searching for.
What i'd like to know is how these parameters act inside Revit.
Which one are handled first?

Jan

you mean in a calculation or reference? That doesn't matter.
A calculation of parameters in a formula handles the same way as excel (Power, Square Root, Multiply/Divide, Add/Substract)
In reference the order of handling is provided by the elements they refer to (Reference Plane, Sweep Path, Extrusion Sketch Lines, Solid Edges)

What sort of parameter you use doesn't really matter from this perspective.

There is no preference applied to one over another. A Shared Parameter is no different than a Project Parameter... a parameter is a parameter. How they are defined and shared between projects and families is different.

A family parameter is confined to the family. It can be seen from within a project but not scheduled or tagged unless it is a built in parameter like those listed under the Identity group.

A Project Parameter is part of a project and applied to categories of families so that it can be scheduled or tagged.

A shared parameter bridges both, acting as a dictionary (shared parameter file) by storing common definitions so they can be reused in other projects or families. When you add a family or project parameter using a shared parameter (definition from the dictionary) it is really just another parameter but it has expanded possibilities because it is "shared".

If you add a family parameter to a door called "My Parameter" and add another Project Parameter to your project called "My Parameter" (applied to door category) and create a Shared Parameter (added to door and project) called "My Parameter" you'll end up with four (4) parameters called "My Parameter" in the project. All will be listed in the properties of the door family in the project. A couple will be listed in the door family itself when open in the family editor. A couple will be available in the Schedule Properties dialog. The name we "see" for a parameter isn't really what makes it unique. They have a GUID (globally unique Identifier).

Short answer...doesn't matter how you add the parameter, Revit doesn't pay more attention to one over another or deal with one kind first, then another...no pecking order.

I've written a lot about parameters over the years on my blog, this POST is one that includes links to other posts.