I have focussed a little so I chose "collect my favourite series" - such as Canadian Tire money (NOT!)
Sorry I just had to write that.
In the past, I've tried to focus on the 1954 series (lots of replacements, tests, errors etc.) Okay so this series allows me to cheat a little!
I believe focus for ones collection is really important, however difficult that may be... I've just tried to eliminate higher denominations & whittle down series that no longer interest me.
Most importantly, notes that allow you to tell a story...
When one finds a note- this is what happens & an easy way to bump one off track! A note that tells a story is always a keeper for me and one of the reasons I've eased up on the condition of a note. A note that shows well is important to me.