1. I was thorough with JSR 168 spec, you will get around 22 questions from here. No need to worry about IBM APIs at all, since no questions will be asked about IBM portlets.
2. From RAD 6.0 Infocenter concentrated on how to test, debug and profile portlets.
3. In sg246681.pdf, concentrated on chapters 8, 11, 12, 19, 20, 26, 30, 31.
4. Know the structure of themes and skins and how they can be customized. Portal 5.1 Infocenter should be good enough for this.
5. Portlet catalogs - This was worst part. I did not find any documentation for this. I did not find the site http://catalog.lotus.com/wps/portal/portal
much user friendly. You will get 1 or 2 questions on this.
6. I didn't spend much time on struts and jsf portlets. My work knowledge helped me in sailing through.
7. For cooperative portlets, I had gone through info center and 0412_roy-CooperativeStandardPortlets.pdf.
8. For portlet service, I had gone through sg246681.pdf and 0509_chen-Tutorial-PortletService.pdf
9. Go through the Portal Admin console to get a feeling of where to find what
10. Try to get as many mock exam questions as possible. Most of them will repeat. Few questions can be got from Cameron's site.