Although we don't believe in timing the market or panicking over market movements, we do like to keep an eye on big changes -- just in case they're material to our investing thesis.

Expect a strong start to the stock market today, as the Dow Jones Industrial Average (^DJI -0.98%) is set to rise by 56 points at the opening bell. Stocks look set to end 2013 near all-time highs, sitting on an overall 24% gain with just a few trading days left in the year. Meanwhile, news is breaking this morning on several stocks that could see heavy trading in the session, including Apple (AAPL 0.52%), Tiffany (TIF), and Darden Restaurants (DRI -0.04%).

Apple shares are up after the company finally inked a deal to offer its phones to China Mobile's nearly 800 million customers. The Mac maker announced over the weekend that it will begin selling the iPhone 5S and 5C models on China Mobile's massive 4G network on Jan. 17. In the statement, CEO Tim Cook hinted at aggressive plans to deliver millions of devices into the market in 2014, saying that Apple hopes to ring in the Chinese New Year by "getting an iPhone into the hands of every China Mobile customer who wants one." To make big inroads in that market, however, Apple will have to go through Samsung, which dominates the country with a 21% share. Apple's stock is up 3.3% in premarket trading.

Tiffany lost an expensive court battle over the weekend that will cost the company more than $450 million. After an arbitration panel found that it was at fault over a failed deal with the Swatch Group, Tiffany will have to take a roughly $300 million after-tax charge to its fourth-quarter results. The total penalty weighs in at more than the retailer's entire net earnings last year. Tiffany expects to fund the payment with a mixture of cash and debt that will reduce full-year earnings by roughly $2.30 a share, but should have no real impact on its business going forward. The stock is down 3% in premarket trading.

Finally, Darden Restaurants has another activist investor on its hands. Starboard Value recently bought a 5.6% stake in the struggling restaurant operator, according The Wall Street Journal. The fund plans to push for a bigger breakup of the company than just the spinoff or sale of the Red Lobster business that Darden announced last week. Instead, Starboard reportedly wants Darden to reorganize by first splitting its real estate holdings into an investment trust before regrouping its restaurant portfolio into high-growth and low-growth divisions. The stock is up 2.3% in premarket trading.