This is a quick, useful video that describes some of the high level keys to a successful CRM implementation. 

There are a many more things to consider that can sink an implementation ranging from technical, process and organizational issues.

However, the three things they identify are very important and worth highlighting.  Find out more at http://www.salesforce.com/learn for more best practices.

[youtube=http://www.youtube.com/watch?v=PvZ-Ky3xrW0]