I'm setting Arch Linux and I'd like to modify the standard dock bar, which is the file that I should edit?
EDIT: like this

I don't want to use docky
I'm setting Arch Linux and I'd like to modify the standard dock bar, which is the file that I should edit?
EDIT: like this

I don't want to use docky
Panel settings are saved here ~/.config/xfce4/panel but you could also try the xfce4-settings-manager.
And to learn how it works you can just download many nice looking examples from here http://xfce-look.org/ and look into the config files that come with these themes.