According to Noozer :
When you run grounding electrodes at the garage, you don't need
to run a ground wire from the house.

Everyone keeps mentioning grounding electrodes, yet nobody I know of has had
to do this. Also, there is no mention of this in the city's wiring guide.

(I'm located in Calgary, AB)

City wiring guides aren't going to cover things like this.

Get a copy of Knight's "Electrical Code Simplified", it's under $20 from
most hardware or big box DIY stores. The Ontario one is Orange. Yours
is Green:

http://www.psknight.com/

[I'm located in Ottawa ;-)]

You will most likely want to run three wire to the panel, and then install
your own grounding electrodes at the garage. That's what mine has.

Trying to use the main panel's grounding is somewhat problemmatic, and is
best avoided in separate outbuildings. Highly difficult with current codes
to pass muster.

- What gauge wiring should I run, considering the distance from the panel
to
the garage?

Check with an inspector. The wire is expensive, and you may want to
consider using aluminum for the feeder - as long as it's done right
(proper greasing and fittings) it's perfectly safe and will save you
considerable $$.

[My 100A 120' feed is #3 Al. Which saved something like $350 over
#4 copper]

I hadn't considered this. I'll need to contact the city to find out if there
are any special requirments.

Will this require special breakers in my main panel? Will I need to do
anything special on the panel in the garage?

If you use Al wire, you have to make sure that everything it connects
to is rated for Al, and grease the connections with the appropriate
gunk. In my case, the electrician ran a #4 copper stub into the main
panel (presumably the panel branch connectors weren't rated for Al),
brought it out to a 6x6 box a foot away, and spliced it there
with split bolts (properly rated for Al-Cu & grease & tape) to the
Al feeder. At the garage end, the panel main connectors were rated
for Al, and only need to be greased.

More fuss than straight copper, but at today's copper prices,
a huge cost saving.

[I'd never use Al for regular branch circuits. For stove/panel
feed circuits with proper care, yes.]

It was an ordinary 100A dual breaker in the main panel (20+ year old
Sylvania Commander). At the garage end, it was a brand new 100A
Siemens panel pack from HD I think.

Be aware that 60A and 100A dual branch breakers for older panels
have become somewhat rare and are often pricy beasties. I lucked out
with the 100A, the electrician gave it to me out of his junk box
for free. The last 30A Commander dual I had to buy was ~$80.
Once you see how much one costs new (if one is available at all),
you might consider visiting flea markets. They often have
whole panels you can cannibalize for their breakers.

Theoretically, you only need a breaker on one end of the subfeed, but,
I don't like omitting the breaker on the main, and a "panel pack" with
main breaker is cheaper than piecing it together without one.

[While I do/did almost all of this wiring myself, the panel feed
itself I had done by an electrician because a minor goofup can be
hugely expensive. He was a friend, and he did it cheap ;-)]
--
Chris Lewis,

Age and Treachery will Triumph over Youth and Skill
It's not just anyone who gets a Starship Cruiser class named after them.