I am a helpful guy. Try to help whenever possible. But I limit my help to resetting a device or offering some advice and never try to fiddle with a System I'm not responsible of. I wouldn't want someone trying to fix a problem a normal user usually can't fix due to permissions on my System, so I don't try to do it on others.
Other than that, it's nice to help and sometimes you get something in return (like getting your food ahead of others for resetting their DSL modem, etc...).