4. http://www.changedetection.com/ (Many alternatives available.)

Another great site for monitoring website updates. It highlights what specific entries have been added or removed, and it's great for monitoring small website adjustments or and seeing what text specifically changed. Unfortunately, it only monitors the site once per day and at a certain time, so you won't know about the many other possible changes have happen throughout the day (like if the website is undergoing maintenance or text corrections so you may miss some important tidbits.)

It is very useful though for getting advanced Press Releases before they are automatically emailed out, finding out recruiting changes (if positions are filled) or new recruiting jobs available, website changes like when Rockstar redirected all of their domains (which in turn indicated a major shakeup within the company), monitoring old comments or forum posts for changes, monitoring specific accounts (old forum accounts) for changes, watching Gaming Publisher sites for new changes (or "hidden upgrades"), etc.

5. Special Announcements

Speaking of monitoring Press Releases, you should also sign up on publisher websites to automatically receive new Press Releases or Special Announcements. This guarantees that you'll be aware of new information before anyone else (most gaming news sites and blogs already do this, but it takes them longer to get the information out). You should also sign up for news & events on the Investor Relations sites.

The Press Release pages should also be monitored, because occasionally there will be new updates, but automated emails are not sent out. :)

6. Trademarks - USPTO.GOV

Great for finding out game titles months in advance of release or announcement.

Unfortunately, this can't be automated (unless through scripting) so you have to manually search the database for new information.

Outside of Google Alerts, this would be your other bread and butter. Typically, most video game registrations are made in the US first (where the publisher is based.) The Mexican, Australian, Canadian, and European Trademark Search Databases are useless, they lag behind the American based system by weeks or months (and they're missing many US trademarks) so there's no point in using those as a source of information. And, the UK one is just terrible.

The Korean TM Database is a pretty good one, though.

When using USPTO.GOV, if you don't want to specifically search for an Owner (e.g. "Blizzard Entertainment") you could do an "ALL" Search for the keywords "Computer game" or "Computer Software" to see all new Trademark registrations.

This is actually a very fun way of finding out new game titles. You'll have to comb through all of the titles, or look for specific wording like a new Pokemon reference for example. (Make sure you confirm on Google, though, to ensure that no one else has already reported on it though. It might be old information.)

Trademark owners may also have patterns to their registrations. For example, I've found that a lot of trademark registrations happen between May and September. And then things are quiet between mid October and February of the following year. It depends on the TM owner though, and it's something you have to monitor.

If you were a blogger back in 2005-2008 and knew about trademark database searches, you would have been viewed as a GOD knowing all of the new and upcoming game titles months in advance. It wasn't actually until late 2008 and 2009 that people started cluing into TM and Patent offices being a great source of this useful information.

* UPDATE:

Here are some Keyword Searches that you can do yourself under Search Marks > Basic Word > Field: Owner Name and Address

blizzard entertainment
electronic arts
activision
take two
ubisoft
zenimax
bethesda softworks
nintendo
sony
sega
thq
microsoft
square enix
valve corporation (careful with this one, you'll get other companies)
konami
capcom
namco
atlus

When searching for new updates, just keep a mental record of the total Record counts. For example, "Blizzard Entertainment" has 83 records. Whenever that number changes, that's when I scan manually for any new changes. This way, you can go through as many companies as possible. (Keep using the back button to return to the search box.)

7. Copyright Searches & Ratings Approval Boards

This information is farther behind trademark registrations, but it can give you more information about what's in the game.

British Board of Film Classification (BBFC)

Search specifically: http://www.bbfc.co.uk/search/?searchwhere=db&q=blizzard+entertainment
Search all video games: http://www.bbfc.co.uk/search/?searchwhere=db&q=digitalmedia

And here are some others to help you out:

Australian Classification Board
All of the most recent Australian entries (very useful)
Motion Picture Association of America (MPAA)
US Classification and Rating Administration
US Entertainment Software Ratings Board (ESRB)
Pan-European Games Information
Singapore's Media Development Authority

8. Recruiting Practices

You can sometimes get a good sense of a game by the types of art a recruiter is interested in. For example; Kenny Carvalho, the Blizzard Titan recruiter, stated that:

At least for me (Blizzard), I look at portfolios before I ever open a Resume. If I see something that looks impressive or shows potential, I will then look at the Resume to see if my analysis of the portfolio makes sense. I wouldn't worry about what game(s) or companies you are or have worked at. Keep your personal portfolio moving forward and you will be fine.

So the first thing he looked at was their portfolio, before even reading the resume. And who specifically did he apply this method to? The following artists who were hired to work on Titan.

Matt "Empty" Taylor
Michael "Orb" Vicente
Laurel "Tully" Austin
Rory "Rory_M" McMahon
Travis "Darkrusader" Castillo
Joshua "Moof" Anderson
Matthew "mheyman" Heyman
Philip "PhilipK" Klevestav
Joshua "Moof" Anderson
Artem "X-Convict" Volchik
Paul "Autodestruct" Richards
Vadim "Slipgate" Bakhlychev
Martin Holmberg
Bram "Peris" Eulaers
Nick Carver
Vitaliy Naymushin aka Rawkstar
Renaud “Guntharf” Galand

If you search their art and portfolios, you may notice a recurring trend from all of the artists. Of all potential artists out there who applied for a job with Blizzard and with all of the different styles, he selected the portfolios that had scifi, armor, robots, ancient cities, and dinosaurs. They must have seemed like a good fit for the Titan project?

It's sort of like information research. If you start working on a new game, and then suddenly the company is researching World War 2 era information or hiring historical experts on related subject matter, chances are that it's a WW2 style game.

9. Other Sources of Information

When searching through resumes, keep in mind that most employees are well aware of keeping confidential information off their public profiles. However, contractors aren't so careful. Search for resumes belonging to Voice and Body actors and for smaller developers they often outsource graphics and audio work to outside contractors as well.

Many resume searches can't be found through Google, so you need to find professional Job Search Databases where you can search through resumes as a potential employer. Target the Actors Jobs databases in particular.

Look for voice actors in other countries, the ones who provide language translations. This is a highly untapped market, and if there is voice acting in Titan for example, you should see multiple voice acting jobs in other countries (China specifically) appear as the game gets closer to the heavy content/lore build out stage. (Unfortunately, by posting this tip Blizzard might be better prepared now.)

Listen to Shareholders calls very carefully, get a recording, and try to obtain the transcript. They often contain a lot of information that are missed by gaming news sites. I've seen it happen MANY times: they only report on official News Releases, but they don't pay attention to little bits of information stated during financial calls. They rely on you and smaller blogs for that type of information. You need to know your subject matter first to know what to listen for.. so try not to look for leaks on too many games, only do it for the developers or games that you love to play.

Will continue to add on to this, there are some other approaches but I just need to decide which to share or not. :)