I went with mining & jewelcrafting, since that feels sort of elemental to me; harvesting minerals from the world, and using it to empower myself and my allies.
Although I’m sure it is possible to come up with an explanation to make any profession suitable 
You could, for example, go with first aid… Perhaps a shaman who makes bandages imbued with healing properties (since bandages in-game actually do heal…).
Or a blacksmith who imbues his work with elemental defensive or offensive qualities…
(Same works with leatherworking and tailoring.)
Enchanting could be imbuing a wider range of items with elemental power.
That sort of fits for engineering as well; improving gadgets & thingamajigs with elemental power. Explosives, for example, are literally elemental power unleashed.
Considering the Draenei’s faith and their connection with the Light, maybe inscription? Empowering allies with written words… (Or perhaps these scrolls are agreements with elementals? ‘For X minutes, I will empower the person who envokes this scroll.’
Alchemy offers some techniques for turning a material into something else, which I imagine is quite interesting from an elemental perspective
As for do’s and don’t’s, I refer to YouTube and “How RP shaman” I find those very helpful, but there are probably text guides on the internet, as well.
From what I’ve gathered, a shaman needs to be on good terms with the elements, so maybe spend some time performing shamanistic rituals or… doing things for the element(al)s? 
(I see no problem with the shaman character doing this in their off-screen time 
)
Apparently, it is possible to force the element(al)s to help, but it’s considered evil by the ‘good’ shaman - and by the elementals, so maybe don’t go down that road unless you want to RP an evil, persecuted shaman 
