IBM has uploaded several videos which walk you through some of the Tips and techniques to achieve Maximum performance
IBM Cognos BI - Designing Reports for Performance - Part 5
http://www.youtube.com/watch?v=c170hFlmdWA
IBM Cognos BI - Designing Reports for Performance - Part 1
http://www.youtube.com/watch?v=OiRvUrUTs-c
IBM Cognos BI - Designing Reports for Performance - Part 3
http://www.youtube.com/watch?v=zLS26-zKsCI
IBM Cognos BI - Designing Reports for Performance - Part 2
http://www.youtube.com/watch?v=QiIIPlaCMOU
IBM Cognos BI - Designing Reports for Performance - Part 4
http://www.youtube.com/watch?v=XbSbXoxxzeA
IBM Cognos BI - Designing Reports for Performance - Part 5
http://www.youtube.com/watch?v=c170hFlmdWA
IBM Cognos BI - Designing Reports for Performance - Part 1
http://www.youtube.com/watch?v=OiRvUrUTs-c
IBM Cognos BI - Designing Reports for Performance - Part 3
http://www.youtube.com/watch?v=zLS26-zKsCI
IBM Cognos BI - Designing Reports for Performance - Part 2
http://www.youtube.com/watch?v=QiIIPlaCMOU
IBM Cognos BI - Designing Reports for Performance - Part 4
http://www.youtube.com/watch?v=XbSbXoxxzeA