Hi:
Exam preparation options are outlined on the certification site:
http://support.sas.com/certify/prep/index.html
As for interview questions, I can only point you to previous forum postings and the various user-group papers on selecting programmers for a job working with SAS.
Since I was a former Literature major, I am very fond of T. H. White's book about Merlin and King Arthur in which Merlin teaches Arthur over and over again that:
"education is experience and the essence of education is self-reliance." Reading about interview questions and being academically prepared for interview questions is different from having experience with the things that are being asked about.
Taking classes, writing programs for your own learning, experimenting with SAS code -- getting real experience with SAS code is the best preparation that I can recommend prior to either interviewing for a job or taking the certification exam.
cynthia