Some of the above causes for duplicate content have very simple fixes to them:
Session ID’s in your URLs?
These can often just be disabled in your system’s settings.
Have duplicate printer friendly pages?
These are completely unnecessary: you should just use a print style sheet.
Using comment pagination in WordPress?
This feature should just be disabled (under settings » discussion) on 99% of sites.
Parameters in a different order?
Tell your programmer to build a script to always order parameters in the same order (this is often referred to as a so-called URL factory).
Tracking links issues?
In most cases, you can use hashtag-based campaign tracking instead of parameter based campaign tracking.
WWW vs non-WWW issues?
Pick one and stick with it by redirecting the one to the other. You can also set a preference in Google Webmaster Tools, but you’ll have to claim both versions of the domain name.