[GNC] How do you tag in gnucash?

[Wm Tarr]

How do people tag accounts / transactions / splits ?

Do you use #ABC[space] for example?  Something else?

I'm trying to leave the question open as I want to get a feel for 
variety and any commonality I might take account of and things I might 
not have considered.

Why? I'm writing an SQL only dimensional query and gnucash doesn't have 
dedicated analysis fields so I need something to pivot on per account / 
transaction / split.

Wm