How do I provide constructive help to inexperienced players in other classes?

[Orophin]

Honestly, without having played a class yourself it's really hard to give suggestions to people on how they're supposed to be playing their own class. There's probably some general things you can pick up on during fights, but as to the intricacies of how a class plays and what abilities it should be using when, that's kinda hard unless you have first hand knowledge of the class.

[Chrysopoeia]

I agree with Orophin; I haven't really played much of the other classes aside from THM so I tend to shy away from giving specific class tips. I usually just give boss strategies based on what has worked in past runs (like, for Copperbell for instance, one good run involved bringing the main boss over to where the other guys tended to go, then wailing on them over there).