Brian Shanahan’s Informita consultancy have a neat, short presentation covering:

• Do you have the right payment terms?
• Are your system terms in line with your contracts?
• Do you pay late, early or on time and is it your fault?
• How do I extend supplier payment terms and protect my brand reputation?
• How do I shorten customer payment terms without losing business?
• How do I measure success?

which contains loads of common-sense and good ideas. For a copy see here.