In my opinion,
American Amber Ale is easy as pie. You want low to moderate hops flavor/aroma with American hops predominant. Flavor should tend toward the malt; emphasize caramel notes more than bready (melanoidin) flavors. Essentially, if you think of an amber American Pale Ale that ratchets back the hops profile and ramps up the caramel/crystal malts, you won't be far off.
I like American 2-row for primary fermentables, with about 10% 60oL and 5% 90-120oL crystals. You can add some American Munich, but using much more than 10-20% puts you more toward an actual Oktoberfest than American Amber Ale. By no means should dark roasted malts be used; not only will it throw off the flavor, the color of the head will suffer. Get your color from caramel/crystal malts. A single-infusion mash is appropriate. You can mash fairly cool, since body, mouthfeel and color come from the caramel/crystal. I usually get ~1.050.
Hops can be any of the "C"s. Personally, I'm utterly sick of them - if I wanted that flavor, I'd just squeeze a grapefruit into my beer - but it's your/his beer. I prefer Willamette. It's just as American, and not so bloody obvious. (Mt Hood is another nice US hops variety.) Plus, and this is just my opinion, since American Amber Ale is really close to American Pale Ale, overuse of "C" hops has the potential to throw off the drinker - she might think she's drinking an APA that the brewer screwed up! I shoot for ~30 IBUs.
Of course you want an American Ale yeast. American Amber Ale has its origins on the West Coast, so yeasts like 1056, US-05, etc. are appropriate. I like Cal V, but your mileage may vary. Ferment relatively cool to mute ester production. Flavor should come from the malts and hops, not the yeast. Perform a thorough diacetyl rest.
Here's the most important thing in the BJCP profile:
Overall Impression: Like an American pale ale with more body, more caramel richness, and a balance more towards malt than hops (although hop rates can be significant).
So, to differentiate from APA, use darker caramel malts to make it richer and darker than APA, and cut the hops back. Easy, right?
Here follows my "starting point" recipe. Your brewery will perform differently, so your actual amounts will differ. I get around 75% efficiency.
Grist:
9# US 2-row
1# US 60oL Crystal
0.25# US 120oL Crystal
Hops Schedule:
All Willamette pellets @ 5% AA
1.25oz - FWH
0.5oz - 20
0.5oz - flameout
Simple, eh?
Cheers,
Bob