Want a strong organization? Just as you might review a staff member at least once a year, every group–nonprofit or for-profit–should put aside some time during the year to assess where the board and where the organization is, relative to where it wants to be.
Presumably you have a strategic plan, and that can provide some good metrics for the process. But in addition each board member should take a good look at the contributions he or she is making, whether their expectations as a board member are being met, and how to work most effectively with board colleagues.
There are a million templates, some so simplistic that they really don’t help much. One I’ve found to be very useful is from the National Trust for Historic Preservation, and it looks at a variety of areas: administrative, governance, and programmatic. Take a look at the National Trust’s organization assessment form and adapt it as you see fit. But make sure the board is taking a good, hard look at itself, so that it can be the best steward possible for your donors and for the community.