From an old proposal but still relevant today IMHO.
1. Consistency of platform, browsers, collaboration and enterprise search strategy.
2. Manage as centrally as possible with a tight team with a means to communicate to the CXOs that have a vested interest.
3. Have a killer backup strategy that meets the needs of your business and make sure it works before day one.
4. End-user training and education in addition to good content and search is the key to end user adoption.
5. Have a Governance and Information Management Plan. Branding consistency with a corporate style guide and consistent taxonomy. Make approved master pages available in site galleries for consistency which will inform users they are on the corporate Intranet.
6. Enforce workflows and approval on document centers and pages where official documentation comes together. Leverage version history and version control to maintain a history and master document that all can refer to.
7. Life cycle managed site collections, and document libraries with information management policies such as Content Types with auditing and expiration.
8. Properly secure corporate assets. Sites with (PII) personally identifiable information should be appropriately flagged and secured and audited.
9. A corporate browse and search strategy for the enterprise will ensure you are making the most out of your intranet assets as well as encourage culture change, best practices and adoption.
10. Platform Usage Policies and development and test environments ensure only the code you want to introduce follows corporate guidelines and will ensure the environment is supportable and able to maintain SLAs (Service Level Agreements).