Nov. 21, 2012 at 3:46 PM ET

Amid all the Black Friday frenzy, it's important to check in with wireless carriers because, at least in this country, they basically dominate cellphone sales. Translation: If you are in the market for a phone — especially Samsung's top-selling Galaxy S III — the following is required reading.
AT&T
AT&T's deals kick off when Black Friday does, 12:01 a.m. ET Friday morning, and runs through Cyber Monday, Nov. 26, "while supplies last." The deals are aimed at online shoppers, and all of them will be gathered on this page for your perusal.
On Friday, the first wave of discounts goes to refurbished phones, which AT&T says will start at one penny. On Saturday, you'll see markdowns on specific phones:
On Monday, there will be more specific models marked down to 99 cents:
AT&T is also having some ongoing holiday-season sales, including $100 off any tablet, even iPads (as long as you sign a two-year service contract); and a Samsung deal that gives people who buy any Galaxy phone "up to $100" off a second Samsung-branded phone or tablet.
Sprint
Sprint's Samsung-focused deals kick in on Thanksgiving itself: Go to the carrier's holiday deal site (or call 1-800-Sprint1) and you can get $150 dollars off a 16GB Samsung Galaxy S III phone — $49.99 with a two-year agreement.
As part of the same promo, you can also get the Samsung Galaxy Nexus or the Galaxy Victory 4G LTE for free (not including taxes and surcharges associated with new lines of service or eligible upgrades).
Sprint also has some pretty good tablet deals going on, too. You can tack a tablet onto your account and get 1GB of data for $15 per month. If you want just the tablet, and have no other Sprint phone service, you can do that too: The $15-per-month starting price gets you 300MB of data. Sprint says it's waiving activation fee on all of its 3G/4G LTE tablets, "for a limited time."
T-Mobile
T-Mobile will launch its seasonal sale on Black Friday, Nov. 23, but the sale runs through Dec. 20, so you don't have to worry about hustling. You do have to worry about collecting your sale price, though: It's a mail-in rebate, so if you snooze, you lose.
Like Sprint, T-Mo's holiday sale centers around Samsung Galaxy phones. Here are the marked-down devices and after-rebate prices (all which require two-year agreements on Unlimited Value plans and Unlimited Nationwide 4G plans):
Verizon
Verizon seems to be least into the holiday cheer (or the Samsung subsidies). When we checked in, the carrier recommended shoppers keep an eye on its deals Twitter feed, and outlined two current deals for pre-paid customers:
We'll keep an eye out for other deals from the wireless carriers, but in the meantime, it looks like the Samsung shoppers on Sprint and T-Mobile are the big winners this Black Friday.
Wilson Rothman is the Technology & Science editor at NBC News Digital. Catch up with him on Twitter at @wjrothman, and join our conversation on Facebook.