You can simply change criteria of the sort or sort by a different column. Hover over the column > click on an arrow and change the sorting > see screenshot: http://screencast.com/t/u8jLvMasIp.
We have a great article in place about sorting and filtering in Clarizen.
Find more information here: http://usermanual.clarizen.com/#2-2-4-3-sorting-columns
For further clarification, please hop on our Intermediate Q&A webinars. These are great resources for visual answers to your questions and free consulting with our experts ( to register> http://www.clarizen.com/live-demo.html#second).