Cartridge alignment tool

All these suggestions are good, but you should know one thing about the Mint - It requires you to line up the cantilever between two minuscule parallel lines and this is very painstaking and, IMO, virtually impossible on a cartridge with a small, tucked-in cantilever.  It's much better for carts like the Lyra with an out-front cantilever.  Just letting you know.  I bought one, but it was just too onerous with my Transfiguration cartridge. 
I just use the gauge that came with my Basis tonearm and it sounds fine.   

@chakster - I have a question for you.  I have an original Denison Soundtractor, which also uses a spindle-to-pivot measuring device.  But unless your arm has a dimple specifically made to be microscopically centered over the pivot, how can you ever be absolutely accurate?  You are going to have to be off by a fraction of a mm, which are the distances we're talking about here.