There are five questions you want to be able to answer with respect to effective resource planning, or managing a portfolio of projects. 1. Should we?
Should we do this project, or this set of projects? Clearly, this is a benefit/cost and contribution analysis. Are these projects worth doing? Are they critical? Are they mandatory?
2. Can we?
This is a capability supply/demand analysis. Do you have the right number of people to staff the project for its lifetime? Moreoever, do they possess the right skill sets? You might have enough people, but you might not have enough DBAs, or EEs, or testers, for example. Having the correct head count to staff a project does not ensure its success if those resources are not functionally prepared to do the work.
3. How are we doing?
Are projects hitting their targets and expectations? Are there gaps in resource-skill supply vs. demand in coming periods? Do we have people available with the right skills to take on the new and unexpected projects that must be done?
4. Did we?
After the fact, you must be able to go back and look at the plans, the intermediate status, and the results, to see how your organization did against those expectations and plans. This analysis must be based on data, not anecdotes or narratives.
5. How do we improve?
Obviously, if you don't have good data, you have little basis for making improvements. Capturing accurate, credible data allows you to develop metrics that help you improve.