A post on Live Search blog provides tips to build your own search engine. The post explains the basic overview of using and creating macros. With Search Macros you can create customized search engines, use them, share them, or discover macros created by the community on Windows Live Gallery.
Discovering that first Macros release was difficult and not very user friendly, the release is updated and has its own homepage and human readable URL. So, this release is much easier to use, bookmark, and send to friends over email or IM.
While you can use macros create by others, the creation wizard helps you to make your own macro without registering or signing in. However, saving and sharing one requires a Windows Live ID.
"You can get started by clicking Edit macros in the More menu on the search results page, or you can navigate directly to http://search.live.com/macros. Many users asked for direct links to create and manage their macros, and we’re very happy to have enabled them in this version."
You can have your own macro in three simple steps. First choose mode after clicking Get Started; next define and test, after defining click 'Save Macro' and you will be taken to your macro’s homepage where you can start searching, email the page to a friend, or share it on the Windows Live Gallery!