A well-regarded handbook on the process of constitution-making has been released (click on this link):
Constitution-Making Handbook (Interpeace, 2011)
It argues that the process of making a constitution is more important than what the constitution itself actually says. It states that the essential guiding principles of successful, modern constitution-making are: public participation; inclusiveness (including gender equality) and representation; transparency; and national ownership.
We can compare whether the process that resulted in the 2005 Constitution in Swaziland was guided by these principles by reading the International Bar Association report:
Striving for Democratic Governance, 2003 (PDF document - quite large)
Look at pages 4-6.