I found this post on the Top Five Marketing Mistakes Companies Make on the Go-To-Market Strategies page. Number 1, especially, fits pretty closely with my own philosophy of marketing, most of which you can find in the Cycle of True Marketing.
Here are the five mistakes the site lists:
1. Marketing without a strategy in place
2. Being inconsistent with your brand
3. Not integrating marketing with sales efforts
4. Marketing something you don't actually deliver
5. Not using the marketing mix effectively
Numbers 1, 2, and 5 are most applicable to libraries. What GTMS says for #1 is especially relevant to us: "The fact is, for marketing efforts to succeed, you must define a target market segment where your product has the most relevance and the best competitive advantage! Most of us can simply not afford to market everything to anyone with the delusion we are the only option for our customers to consider."
The Go-To-Market Strategies site explains fixes for all the problems above. Check to see what you could improve.