I know all the techies out there are gonna cringe, but I have an extension speaker jack on my amp, and I plug in my headphones there and unplug the main speaker. I've never done so for an extended period, since everything I read about needing a speaker connected to the amp at all times has got me pretty freaked out about blowing the amp.
That's all I got fer ya.
... and that's all I have to say about that.
[U]ALL[/U] generalizations are [U]WRONG[/U]
[/sarcasm]