where to put source

[John Dangler]

I guess I'll ask this once more - 
I've downloaded the source of a package that I want to build a .deb for
and submit to Ubuntu for possible inclusion in the repo's.

Searching for how this process works in various distro's, I've
seen /opt, /usr/local/src, and ~/packages/project_name as places to
build from.

Does any one here know which is the preferred location?