Some will find updates and some you will have to figure out on your own. Apps you purchase or download from "App world" usually go into your "My world" and that will let you know when you go into it, if there is an update available for any of the apps you may have downloaded.....
Both App World and the CB App Store (MobiHand) will notify you of an update.
With App World in particular the notification can be delayed by a day or two. I don't know if this is to avoid overloading their servers or just a glitch.
And like dcgore said, you can always check yourself.
In App World go to My World and click on the Apps there. You'll have have the option to upgrade if there is one.
In App Store, scroll down to My Apps in the bottom right corner. Apps with an upgrade will have the green arrow indicating an available download.
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