What's the best way to mount adjustable shelves inside a wood cabinet?
The shelves were made from 3/4" birch plywood.

I was going to drill holes for shelf pins, with a jig made from peg
board. These would be the pins with a flat protrusion on which the
shelf rests. But then there's also the type of pin that's recessed into
the bottom of the shelf (I assume a router is used to cut out the
groove in the shelf bottom). This type would prevent the shelf from
moving laterally.

Another problem is that I made a stupid newbie mistake and cut the
shelves a bit too narrow for the space they're going into. I lined up
the saw on the wrong side of the line and the shelves are about 1/4"
too narrow (1/8" on either side). Will this affect the stability of the
pins or put excessive stress on the wood near each pin hole? if
something heavy is placed on the shelf? If so, is there a solution
besides cutting new shelves (there are only two, so it's not too big of
a deal). Maybe I can glue a 1/4" strip of wood to one side of each
shelf to widen it. Or maybe there's some kind of nylon or steel
spacer/extender that I can place in between the shelf edge and the
vertical member?