The problem with information is that to obtain it takes time and cost money? So how much time do you have and how much should you spend? Have a look at the SEBok, Kerzner, AS/NZS 15288 and the Raymond & Bergeron article to try to get a handle on this issue. You might also like to consider the advice in AS 150 21504 on Project, programme and portfolio management. The theory from 21504 is that information flows from the program up to the portfolio and strategy flows down from the portfolio to the project. Sounds good. But is it that simple? If so then why did BP not implement project, programme and portfolio management and solve their problems