when i m watching a good anime i picked myself i do nothing else while watching. when i m at a friends house and watching a bad anime, talking or eating are the things i do.
I rarely watch anime or read manga in workday.
But when it's weekend (especially saturday night), i often spent my time watching anime all night long in my bed. While drinking, and eating junk food.
I just focus on the chapter/episode. Like eating is fine I guess but subbed anime is difficult to pay attention to if I have say, games running on the side.
When I'm watching/reading something new and interesting I'm focused on it and do pretty much nothing else. Eating snacks or drinking coffee doesn't count. :P
When I'm watching stuff I already know or something boring I'm playing games, surfing in the web, doing pretty much everything else... and then I'm going mad because I missed something, always the same. :D