If an app has an update available, you'll want to download and install that update. For apps you've obtained via
the Mac App Store, this is as simple as launching the App Store app, clicking the Updates button in the toolbar,
clicking Update All, and providing your Apple ID and password when prompted--this will download and install all
available updates at once. For non-Mac App Store apps, you'll need to manually install updates. Some apps provide a
built-in update feature (often accessed by choosing Check For Updates from the application's Application Name menu
or its Help menu); for those that don't, you'll need to visit the developer's website.
The biggest offenders here--in terms of being incompatible with Mountain Lion--will be programs and system
add-ons that integrate with (or hack) OS X at a low level. Kernel extensions, for example, are notorious for being
incompatible with major new versions of OS X, but you may also find that utilities that tweak the Finder, add-ons that enhance Mail, and other plug-ins
and "enhancers" won't work under Mountain Lion, even if they worked fine under Lion. (This will be a bigger issue
for people upgrading from Snow Leopard.) So be sure to check vendor websites for OS X 10.8-compatible updates for
your favorite software before upgrading. (Don't forget to check third-party System Preferences panes and Mail
add-ons.) If it turns out that a particular bit of software is incompatible with Mountain Lion and doesn't have an
update available, uninstall or disable it until a compatible version is released.