Yes, solving previous years' question papers and sample papers are very much important to know how much you are prepared for the examination. Apart from preparing from NCERTs or IPE Textbooks, you can also practice from some standard reference books like HC Verma and DC Pandey for Physics, Concise Inorganic Chemistry by J.D. Lee, Physical Chemistry by P Bahadur, RD Sharma for Mathematics etc. So after completing the syllabus, your first job will be giving mock tests as much as possible and also solving past years' papers. This will help you know the exam pattern, what kind of questions are usually asked in the examination. While giving the mock tests or solving past papers, you 'll find difficulty in few questions. You'll have to analyze them and work on them so that this would not create any problem in the exam day. We have last year's exam papers of AP EAMCET
http://engineering.careers360.com/articles/ap-eamcet-sample-papers
Also Careers360 has free mock test for all AP EAMCET aspirants
http://learn.careers360.com/test-series-ap-eamcet-free-mock-test/?icn=AP_EAMCET_test-series&ici=AP_EAMCET_text-mapping