How do you add a sidebar to a skin

[vb_mp]

If a skin comes in fluid or fixed mode, is there a standard way of adding a side bar? I have seen some people add a siderbar in the header or footer template, but it all seems to be done based on the will of the designer, not following some set of rules?

Do skins usually come with sidebar support? Or does it have to be done as some sort of addon?

mp