In past years, we would have started talking to you about online shopping for the holidays a few days before Thanksgiving.

But as your email inbox and visits to stores may have already told you, online holiday shopping deals kicked off around Halloween. And the shopping frenzy we’ve come to know as Black Friday is now a seasonal marathon that stretches past Christmas all the way to New Year’s Day.

So it’s not just your imagination that the shopping season feels increasingly protracted. And the trend’s not going away. Online shopping sales for November and December are expected to reach $54.5 billion, a 16.8 percent increase over 2011, according to research firm eMarketer, which is closely tracking holiday trends.

The ways people are online shopping are also changing dramatically and 2012 may be the tipping point for a few new options that were just starting to gather steam last holiday season. This year, you can expect to see more people shopping by smart phone and tablet via apps, more deals tied to popular social networks like Pinterest and Instagram, more widespread daily deals from online and traditional retailers, and some new tricks for hardcore deal hunters looking to save some extra dollars.

Here’s a short guide on what to expect.

n Price matching and same-day shipping. Brick-and-mortar retailers used to whine that online sellers like Amazon were destroying their business with lowball pricing and by urging shoppers with smartphones to use brick-and-mortar stores as showcases, then buying online. This year, the gloves are off. Target, Best Buy, Macy’s, Nordstrom and others are offering to match prices against online retailers and offering options like same-day shipping and in-store pickup to level the playing field.

n Shopping by phone and by tablet. The whole concept of Cyber Monday came from bored office workers using their employers’ fast Internet connections to get their Christmas shopping done online. A surprising amount of shopping, though, is now shifting away from the computer desktop and onto phones and, in particular, tablets like the iPad. SteelHouse, a research firm, says that in a survey it conducted of 300 U.S. shoppers, 52 percent of owners say they plan to spend more money this year using their tablets for holiday shopping.

Using mobile devices while shopping has a few clear advantages. You can compare prices with other stores while you’re shopping in person, look up reviews of sale items like HDTVs or video games, or double-check a loved one’s shopping list if they keep it online. Apps and mobile web sites are also useful for getting product recommendations or checking store inventory.

Retailer apps and mobile-friendly web sites in general have greatly improved over the clunky, slow interfaces of the past and so have our mobile Internet speeds.

This year may also mark a change in the way people use coupons with mobile devices. Coupons.com, Valpak, Target and Walgreens, among others, are using Apple’s “Passbook” app on newer mobile devices to make mobile coupons easier to keep track of and scannable in stores.

You can also expect mobile device shopping to be popular when people sit down for Thanksgiving. Jeffrey Grau of eMarketer wryly observed in a research webinar, “People are bringing their smartphones and tablets with them to their Thanksgiving dinner at friends’ or relatives’ homes and using their mobile devices to shop before and after the Thanksgiving meal.”

n Bargain hunters have new tools. Websites like Slickdeals and FatWallet for bargain-hunting shoppers have gotten increasingly mainstream over the last few years and have expanded into social media, apps, and in the case of FatWallet, even a cashback rewards program.

That’s something you can expect to see more this year from credit card companies and upstarts like Shopkick and MyPoints in addition to retailers. Loyalty programs sometimes offer as much as double-digit percentages for money back on what you buy or store credit toward buying items later on like Buy.com’s Rakuten points program.

Some of the more shopping-friendly social media services have also gotten into the act. Users on the aspirational site Pinterest are being wooed by retailers who figured out that Pinners tend to spend more than other customers. The photo-sharing site Instagam has also become a place for brands to connect with customers.

For heavy online shoppers who have to deal with lots of packages, we’ve been intrigued by one new product, Elephantrunk parcel drop, a secure box to send and receive packages from your front door. It works with major package delivery services and is being sold in a test run through Home Depot.

n Our advice. That’s a lot of information to digest, but you can take away this: seek deals both online and in stores, stick to trusted retailers and online deal sites, and pace yourself. Many of the best online deals may not be available until after Thanksgiving. And all those deals happening after Christmas? It’s never too early to get started on your shopping for 2013.