According to zxcvbob :
moose wrote:

As a personal preference (and I think preferred by codes), I'd do
this with a single 12/3 NMW (or UF) and tie-barred breaker, and just
inside the shed I'd split it into two 12/2 branches. You sometimes save
a bit of money, and it's a little easier to install.

I think I see what your saying. Have two (15A?) tied breakers sharing
neutral and ground, with separate hots? That sounds like the best
solution. GFCI is code I assume for the breakers.

Yup.

I was thinking of saying something about GFCI. You _should_ have
it (tho, it might not be explicitly code-required, depending on what
the floor is, external outlets etc).

GFCI breakers are expensive. Bob's solution is better:

At the shed, you'll split the circuit into two branches. One goes to
your electric outlets, and the first one gets a GFCI to protect
everything downline from it. The other goes first to the lights
(without a GFCI) and then to any specialty outlets you might have (like
a freezer that your don't want on a GFCI), and *then* another GFCI
outlet and more convenience outlets if you want.

The above might be a bit confusing. Basically, you put a GFCI in passthru
mode on both branches (MUST be downstream of where the neutral splits).
You just might want to put a few unprotected outlets _upstream_ of one or
both of the GFCIs for things you can't afford to trip (like a freezer).

Note: I believe electrical code can be pretty picky, so you may need
to use non-duplex (_single_ outlet) receptacles for them, and they
must feed "fixed" equipment (like a freezer). Not general purpose outlets.

[I'd probably GFCI the lights. Depends on whether anything in the
shed is going to be "dangerous". I wouldn't GFCI _all_ of the lights
in a workshop with power tools, for example.]

GFCI devices are cheaper than GFCI breakers (especially if you'd need a
2-pole GFCI breaker), and you don't want a GFCI on some things (lights,
freezers, maybe a sump pump, etc.)

Check on adding a supplemental grounding electrode at the shed and
connecting it to the ground wire at the first J-box.

You only add supplemental grounding electrodes to outbuildings that
have a subpanel. Not necessary for a single circuit (the dual breaker/
multi-wire branch counts as a single).
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.