A typical "normally" framed inside corner will have 3/4" & 1 1/2" exposed stud faces for fastening the sheetrock.

A typical "normally" framed inside corner will have 3/4" & 1 1/2" exposed stud faces for fastening the sheetrock.

The answers I'll provide will be assuming you have 1/2" drywall as the wall finish.

A corner is where the interior and exterior walls of the building change directions.

There are a couple of styles of corner framing's.
Two standard studs stood of edge, 1-1/2" apart with blocks placed between them, and nailed together.
The two reveals will be 1/2" and 1" respectively.
Another style, called a mormon corner, is 1 stud lain flat and another stood on edge and nailed together, forming an "L".
Each reveal is equal at 1".

Intersecting walls will generaly have three studs nailed together forming a "U". Each reveal is equal at 1".

Of course you could disregard all this and simply chalk a line at the top of where the top of the 1x cleat will be, or the bottom of the shelf and drive a nail above that line, 1/2 the thickness of the shelf, in the areas you have questions about.

I made some illustrations of corner/partition variations.
Traditional corner-post type of framing corner. Material-intensive and time-consuming.

California corner (that's what they call it in my area). Takes less time.

Traditional partition post for walls that intersect in a "Tee":

Ladder blocking, suitable for tees or corners. Versatile and cheap; allows wall studs to stay on layout, blocking made from scrap.

Wow, I never got better answers than those. Thanks very much everybody!