Usually, I maintain some kind of boilerplate notebook and paste relevant contents into place. If you want to keep it central, you can use a package (.m) file that contains your option settings (e.g. with SetOptions).
On the topic of using/generating packages, see Programmatically generate packages from notebook files?.
You can then load the package with Get or Needs. In your case, you probably don´t need a "proper" package but simply some code you can load conveniently (which works just fine with a .m file).
