I am SCJP6.... and seriously not have much knowledge of even servlet.
How should I start and which server should I use?
Please help me out..
I am still preparing but I believe the following things are helpful:
1. Read the Head First book twice, for my case, I did but still did poorly on practice exam (enthuware)
2. HttpServlet, JSP action, JSTL are basic, so begin from there and ensure that you know them.
3. Software Pattern like MVC, Transfer Object, Business Delgate, Service Locator is simple. just understand them.
4. Really know the hard stuff well, especially about HTTP session, attribute binding, EL, custom tag, tag file, directive, taglib, tld; they get me all the time.
5. In my opinion, the HF book along isn't sufficient because it's too dry to absorb, buy an enthuware SCWCD exam. Yes, yes I know, but would you pay $30 now or to pay $300 bucks later on to find out you are not well-prepared?
6. There is another book which goes like SCWCD exam study kit by Mannings, not as beefy as HF but good comprehensive coverage
so 2 books + 8 mock up tests + some practical coding on a tomcat server (you can skip the custom tag but at least try out HttpServlet) + Many dark, lonely nights in the basement
Security and URL precedence are a bit confusing but try to look for some logics behind the rules, for example, the idea behind all security rules is that "if any one of the admins says you can't access a file, then you can't, doesn't matter what others say", which makes sense from a rather-safe-than-sorry perspective.
Always try to see Why's not just What's. There are a million tiny rules, but there is only a couple of central themes based on rather-safe-than-sorry principle. Try to stay focused on one task and really thoroughly learn that topic before moving onto something advanced like BodyTag or EJB, session bean, (though it would be time to start reading about them ...)
When you finished HF book once, you may start looking for jobs and find out a lot of "Struts" in the job. Good news - you are now in a good shape to learn Struts! it doesn't help with the exam at all but it will help you quite a bit in getting a real J2EE job.