You have safety lines in Encore to let you know what's considered Action Safe & Title Safe. Now with newer TV's these mean a lot less then they did 10 years ago, I pretty much still use the safety's. This way I know that anything I produce will play on any set out there. I wouldn't ever put anything that I needed to show near the edges of the screen.
CRT sets are still by a long margin the most common out in "the wild" as it were, and they *all* overscan to a greater or lesser degree.
Use the margins.
If using Photoshop CS/CS2, use the D1/DV template as well.