Good question:The 990 form is rife with plenty of valuable information on the inner financials of an organization. You don't all of it though if you're researching potential donors. I personally look for the following information:
1) Contact information like phone numbers; sometimes it isn't always listed in other documentation.
2) Assets - gives you a general idea of their giving capacity; also gives you an idea about how financially healthy the foundation is, which impacts their capacity to give.
3) Board list - as you think, it can be useful in tailoring a request but it is also useful in determining if your board knows their board.
4) Guidelines - Usually located at the bottom of page 6; tells you how they accept request letters or if they don't accept unsolicted requests.
5) Grant list - Tells you who they funded and for how much. The later information can help you form an estimate of their average gift size, which might not be indicated in other foundation profiles. Also, allows you to form an opinion on the types of projects or agencies they like to fund.
6) their fiscal year - located at the top of page 1 is a line requesting information on the foundation's fiscal year, which usually run either January 1 - December 31st or July 1 - June 30. This can be useful insofar as you can determine when a foundation MUST expend their charitable dollars, which is by the end of their fiscal year.
