One needs to be very good at this especially the manual testing methodologies. But only knowing different testing concepts is half work done. The next – most important thing is to know which type/technique/concept of testing can be applied at what stage of SDLC.
“What should I test and when” is very important. There might be some concepts, which are not applicable to what we, professional test in our company, but it’s always better to have an idea of all testing practices.
Many freshers and working testing professionals have might not worked on various testing domains like localization testing, time Zone testing etc. But knowing more than what you have worked on will help you better answering the different questions from the interviewer. I always try to keep my testing knowledge updated besides my current project work. This helped me a lot while switching my job some years ago. What if an interviewer asks you question on topic, which you have never worked on? For example you don’t have any experience on web based projects or client server testing and interviewer asks you to test “Yahoo mail application”. Will you be able to answer this question? You can. Even you have not worked on this type of projects. How? Your curiosity to learn the things you never done before will help you in this case. So broaden your thinking area, be curious in every work and every query you face in your daily work routine.
Knowing more is harmless and will definitely help you at least to give your thoughts on the questions asked by interviewer.
The very essential part of a test engineer is “Thinking out of box”. If you are not capable of thinking out of box, believe me testing is not for you. What do you mean by thinking out of box? Don’t just follow the traditional methods. Implement new things in testing. Try to summarize, automate the routine testing work. Think from user perspective. Think how user will use your application. What common mistakes he can make or which tasks he can perform on your application? This way you will get insight of any application and will also help to answer the questions in depth.
Most importantly you need to be perfect in what you mention in your CV. All the questions interviewer asks will be based on what you are specifying in your CV. So do not mention the skills you have not worked on, just for the sake of decorating the CV with multiple skills.
If you don’t know answer for a question, say so. Don’t fool around and get into trouble.