In an hour or so, a few hundred technology journalists–along with analysts, Apple employees and various invited guests–will stream into an auditorium in San Francisco’s Moscone West convention center. The occasion is the keynote opening Apple’s Worldwide Developers Conference.

For once, the subjects of Steve Jobs’ keynote aren’t a mystery–Apple announced last week that it would cover iOS 5, the next version of the iPhone and the iPad’s operating system; Lion, the next release of Mac OS X; and its upcoming, still-undefined iCloud Web-based suite of services. But the style and content of the keynote (or “Stevenote” in the vernacular) shouldn’t be a mystery either.

Having covered more than few Stevenotes myself–for example, Macworld 2008, the introductions of the iPad and iPad 2, and last September’s relaunch of the Apple TV–I’ve gotten reasonably familiar with the genre. Here are a few things to watch for in coverage of today’s keynote, and in the video Apple will post on its site later today if it sticks to standard practice.

(To my fellow tech reporters covering it live: Good luck with the wireless! You’ll need it.)

• The how-we’re-doing summary: Jobs keynotes often lead off with an upbeat recap of all the different ways that Apple has excelled, including data about iPhone sales, an update on the App Store’s inventory and sales, and a slide show of Apple’s recent store openings.
• Trash-talking the competition: Next, you may see Jobs discussing how the competition has wasted its chance, building out a theme of “we may not be first to this market, but we’re going to be the best.” Watch this part and read any live coverage of it with great skepticism–it’s easy to filter out inconvenient statistics, and outright misquotes have been known to surface here.
• Demo time: Jobs and a succession of product managers from Apple and other companies will show off how the new software or hardware looks and works. It’s easy to rig a demo–but because Apple refrains from showing off things it isn’t ready to ship, these are reasonably credible exhibits. But watch out if the WiFi melts down as it did in last year’s WWDC.
• Promises of third-party support: The reality distortion field can get especially thick in this section, when Jobs and executives from Apple and other companies outline how the entire industry is coalescing around Apple’s new software, service or standard. But other firms can be stubborn, especially if they already fear Apple’s influence in a market sector: Nine months after the Apple TV debuted, in distinct contrast to early estimates from analysts, you don’t have a better selection of major networks renting shows on iTunes.
• Optional nods to open standards or open source: Apple likes “openness” in principle, so it often touts that as a virtue in its products. Sometimes it’s for real: Apple not only built its Safari browser on the open-source foundation of KHTML, the company has since greatly improved its resulting WebKit open-source code base and brought it to smartphones–so if you use an Android, webOS or BlackBerry 6 phone, you can thank Apple for its browser. But at other times, the promises of openness in a Stevenote vanish in practice: A year after Jobs pledged to make FaceTime video calling an open standard, it remains closed.
• Ship date and price: Unlike too many other tech companies, Apple doesn’t leave the audience guessing. Jobs will name a price and a date for the hardware, software or service being introduced. And the company almost always sticks to them (unless it’s the white iPhone we’re talking about).
• Video break: Having outlined what a great product Apple has, Jobs will sometimes screen an ad or marketing video making the same points. If it’s an ad, he may even play it twice after saying something like “Wasn’t that great? Let’s watch it one more time.”
• “One more thing”: Jobs loves to save one last surprise for the tail end of the keynote. My guess is that the odds of an OMT are a little higher this time around, since Apple has already outlined the main points of the keynote–why take all the fun out of the guessing game?

On that note, here’s this post’s “one more thing”: Remember that Apple isn’t always as big on incremental upgrades as other companies. You could consider that a downside of its intent on showing off new releases in a finished state. But either way, don’t buy its latest iThing thinking that subsequent maintenance releasees will quickly  fix what’s missing from it. Apple might grant your wishes in the next major yearly update–but that’s a long time to wait. And by then, you’ll have a new Stevenote to tantalize you.

Update, 5:39 p.m. You can watch the nearly two-hour keynote on Apple’s site if you have its QuickTime software installed. I’ve also fixed some spellcheck-proof typos in the first version.