You will need a 10mm hex for the back 2 differential plugs. A T-70 torx bit for the front differential plug. and a 8mm hex bit for the ATF drain plug.
Spray some penetrating oil on the bolts the night before to make your life easier.
The rear diff is pretty straight forward, unbolt the fill plug, then the drain plug. Once it's all drained, bolt up the drain plug. Both had crush washers on mine, so get those from the dealer if you want. I used the old ones though and they're not leaking. But if I knew they were there, I would've got new ones. Use a pump to fill the rear diff until its overflowing. Then bolt up the fill plug and that's done.
For the front diff, use the T-70 torx to open the drain plug, and for this one you're gonna want to measure what comes out. I used a cheap bucket I found at walmart that has measurement lines by the quart on the side, and dumped the drain pan into the bucket to see how much. After it's drained, plug it back up. This bolt had a crush washer on it as well. Put in as much new diff oil as what you took out through the diff oil dipstick tube. I used the Mobil 1 synthetic 75W90 and it took like 2.6 quarts for the front and back.
For the ATF, use your 8mm hex to unbolt that and drain with the same procedure as the front diff. Measure what comes out, and put the plug back in. I did have a new crush washer for this one, because I knew one was there. Put new ATF fluid in the ATF dipstick tube, however much you took out. When I did mine, a little over 4 quarts came out. I'm going to do the ATF again this week and next week, and I figure if around the same comes out both times then most of the fluid should be replaced by the third time. I used the Subaru ATF-HP as the fluid for this.
Let me think what else The car should be level for filling, and for draining I just manipulated the height of the corners to help drain out whatever I was draining at the time. Fluids should be warm when draining. So I drove around some before doing the differentials. Then I drove it around again before doing the ATF. Get you some latex or whatever gloves, and shop towels. A long flexible funnel works good for filling the dipstick tubes.
I guess that's all I can think of, but you can ask whatever, because we have the same car, and I just did mine last weekend.