Hello,
I have been looking and looking and I can't find anything that tells me how to 'pool' something in reaper. Lots of stuff about once it's there, or how it should be improved... but I haven't the foggiest how to just get started.

Could someone please help me find the appropriate documentation, or forum post, or something that might give me a hint?

Thanx for any help you can give.

And yes, I do kind of suck where internet searches are concerned... I never really got the hang of it, I think. I must be asking Google the wrong questions.

For midi clips, just ctrl-shift-alt drag and you will get a pooled midi clip. This was added in v4, prior to that there was a clunky workaround where you had to save the midi clip to file first and many of the older posts in the forum probably refer to this obsolete method.

AFAIK you can't do pooled audio clips. If you copy an audio clip, the new clip references the same audio file, but you can't set things up so that a fade adjustment, or pitch change will automatically propagate to another 'pooled' audio clip.

In preferences->media->midi there's a checkbox for "Pool MIDI source data when pasting or duplicating media items" that when checked created pooled items if use copy/paste (ctrl-c,ctrl-v).

If you want to change reaper's behavior so that a simple ctrl-drag creates a pooled midi item, go to preferences->Editing Behavior->Mouse Modifiers --- Context: "Media Item / left drag" and swap the behavior for Ctrl and Shift+Ctrl+Alt.

Like swivel says, set as you wish using mouse modifiers. I have for example ctrl-drag to create normal copy, alt-drag to create ghost copy.