I keep mine on a side table in the living room so whenever it's not there and not in my hand, then it's lost. If I spend some time searching, I'll usually find it on the kitchen counter, camouflaged against the black leather couch, hiding beneath a pillow, or sitting somewhere I could've sworn I didn't put it. And if I still can't find it, then I call it from another phone, crossing my fingers that the ringer is on.
But now that I've installed what I would definitely call a must-have app, I never have to worry about the ringer mode on my EVO when I can't find it.
And it's all thanks to alienmanfc6's Wheres My Droid, which can be found in Android Market.
What it does is let you set an "attention word/phrase" that you send to your EVO via text message to automatically disable silent or vibrate mode, turn the volume up, and start ringing. The phone will ring for 30 seconds, 60 seconds, or 5 minutes (depending on your chosen settings) and can return the volume level back to its original setting after the EVO is found.
The downsides are that the ringer mode doesn't get reset (so if it was silenced for a reason, be sure to re-silence it afterward), you need access to something that can send a text message, and of course it works best when used in quiet environments. Don't mistake this for theft protection either; there is a GPS option in the settings for use if GPS is already enabled to begin with, but there's no remote wipe function.
For finding your misplaced EVO at home or a friend's/relative's house, however, Wheres My Droid is pretty invaluable.