Thanks to all dear ranchers for their wishes. Here is my little story on the preparation.
Initially I used the Head first servlet and jsp 1.4, later on switched to 1.5 version. Read it completely for 2 times first. Then I started taking the various online mock test, (note: not the one given in book) like marcus green's emulator etc.
Then I used Javaranch to have the experience of the fellow ranchers, and almost everyone suggested to look at the APIs, EL, design pattern and tags. Thats very much true when you give the exam. Straight forward questions are very less and mostly the scenario based question (like if you are developing a website and you caught up in a particular scenario.)
Downloaded the APIs from sun docs, JSTL specification pdf and Peabody's design pattern notes. Used all of them regulerly. Meanwhile I used my own coding to resolve any doubt and used Javaranch to get helping hands as well.
Finally, a day came when I muster up the courage to give the HFSJ1.5 mock exam, and was right at the crossing line. After nearly 10 days of that mock exam I gave my certification.
Tips: 1. follow the directions of HFSJ word by word (if they say in jstl chapter to download the specification, do it ) 2. Know servlet and related API by heart. 3. Must do 1.4 version mock exam.