It's that time of the year again. On Wednesday, Apple (NASDAQ:AAPL) will host a "Special Event" in the Steve Jobs Theater at its new campus in Cupertino. During the event, the tech giant is expected to unveil its latest version of the iPhone, along with other new products.  

The stakes are high going into the event. Since Apple's iPhone X unveiling last year, Apple stock has surged 35% as trailing-12-month revenue and earnings per share soared. Can a new suite of products help Apple keep impressing?

When Apple executives take the stage on Wednesday, here are three things for investors to look for.

Apple customers holding new iPhone X devices on launch day

Image source: Apple.

iPhones

The main announcement on Wednesday will likely be the company's annual unveiling of its latest iPhone models. At the event, Apple is expected to show off three new iPhone models: an upgraded version of Apple's current 5.8-inch iPhone X, a larger version of the iPhone X with a 6.5-inch display, and a lower-cost version of the iPhone X with a 6.1-inch LCD screen (the other two iPhones are expected to have OLED displays). 

iPhones are obviously key to Apple's business. In the company's most recent quarter, iPhones accounted for $29.9 billion of Apple's $53.3 billion of revenue during the period. In addition, iPhone revenue rose rapidly during the period, rising 20% year over year. 

Wearables

Rumors suggest Apple is ready to capitalize on the strong momentum it is seeing in wearables, with new versions of its Apple Watch and possibly AirPods, too. Accounted for in Apple's "other products" segment, fast-rising sales of Apple Watch and AirPods helped the segment's revenue rise 37% year over year in the fiscal third quarter.

To replace its previous Apple Watch, Apple is expected to launch an Apple Watch Series 4, which is rumored to have a slightly wider screen thanks to narrower bezels.

Apple Store employees stocking shevles with Apple Watch bands

Image source: Apple.

Though there hasn't been as much buzz for the potential unveiling of new versions of Apple's popular AirPods as there has been for an Apple Watch Series 4, new AirPods are certainly possible. When new versions of AirPods are released, they're rumored to be water resistant and boast "Hey, Siri" voice assistant activation.

Services

Beyond potential product announcements at Apple's event this week, investors should also keep an eye out for new or enhanced services. Services has become Apple's second-largest segment (behind iPhone), accounting for 18% of revenue in fiscal Q3 -- up from 16% of revenue in the year-ago quarter. With fiscal third-quarter services revenue up 31% year over year, the segment is critical to Apple's growth story.

It's not clear whether Apple will have any updates relevant to its services business on Wednesday, but the segment's growing importance to the company's overall business makes it a narrative worth watching.

Apple's event begins at 10 a.m. PDT on Sept. 12. A live stream of the event will be available on Apple's website

Daniel Sparks owns shares of Apple. The Motley Fool owns shares of and recommends Apple. The Motley Fool has the following options: long January 2020 $150 calls on Apple and short January 2020 $155 calls on Apple. The Motley Fool has a disclosure policy.