Walls and Ceilings - Shelves on plaster walls

I am trying to install shelves in my closet, which has very old plaster walls. I am afraid that the walls will not be able to hold the shelves and was hoping that someone would be able to give me a suggestion or two about how to go about it. I have tried to find the studs, but have had a very difficult time locating them in the small space.

The studs should be on 16" centers, but in an older home, the framing studs may be on 24" centers.
You won't be able to find them with a regular magnetic stud finder in a plaster wall.
Measure around and use a small drill bit to try to find the studs, and anchor the shelving brackets in the studs (at least as many as you can).
You can also drill larger holes and use molly bolts or butterfly bolts in the plaster walls.
Good Luck!
Mike

Another way to find studs is to look for nail head indentations in the baseboard near the top edge. It was likely nailed to the studs near the top of the baseboard.