My Scottish Fiddler friend says - If you can say Rangers Celtic Rangers Celtic in time with the music , its a reel (4-4) and if you can say Liverpool Everton Liverpool Everton in time , its a Jig (6-8)
and Liverpool Everton Manchester Liverpool Everton Manchesteris a Slip jig in 9 - 8 !

^^^^ Tell your Scottish fiddler friend he's genius. :)

The best & simplest way I've ever heard it explained.