How to tell what clickies and procs stack or not?

[Tipsyer]

If you look at the spell info on the wiki, the numbers on the left side under the details section that explain the benefit should be the spell slot.

Spirit armor > turtle skin
Guard > spirit armor
Lesser shielding should stack with all the above.

(I'm 90% positive this right, but it's been awhile).

When in doubt, test them yourself.