How do I figure out the right pronunciation for transitions?
It would be nice if there were an authoritative, canonical, source for these sorts of waypoints, but sadly, I don't think one exists. I say that because I hear controllers sometimes using a different set of vowels or syllable emphasis "today" than they did "yesterday". If there were a single "right" way to verbalize CNERY or SCTRR, I'd expect ATC to have them all down. But in plenty of cases beyond those two, it remains unclear. 

For example, the JFRYE arrival into Dallas -- is it the "Jeffrey" or the "J-Fry" arrival? You hear both from Ft Worth Center all the time.

My conclusion: no cannonical source exists.