Have you used automatic testing tools? Which ones?
If you never have seen automation tools before, do not try to fool around the interviewer. You produce a bad impression when "caught" on lying to the interviewer. However, if you ever used the automation tools, it would be a huge advantage for us to mention them even if those tools were proprietary automation tools of your previous company. Be prepared then to answer general automation testing questions.
How would you build a test with WinRunner? Rational Visual Test?
First of all, see the comments to the previous question. Then, all automation testing tools I ever heard of have a GUI recorder which allows you to record the basic user interactions with the software underneath. Then, you manually update your initial script to suit your needs. You must know scripting language of the automation tool for that.
Could you test a program 100%? 90%? Why?
Definitely not! The major problem with testing that you cannot calculate how many errors are in the code, functioning etc. There are many factors involved such as experience of programmer, complexity of the system etc.
How would you test a mug (chair/table/gas station etc.)?
First of all you must demand requirements and functional specification and design document of the mug. There will find requirements like ability to hold hot water, waterproof, stability, break ability and so on. Then you should test the mug according to all documents.
How would you conduct your test?
Each test is based on the technical requirements of the software product.
What is considered a good test?
Good test is a test covering most of the object's functionality.
What is considered a successful test?
A test that discovered more errors. The whole purpose of testing process is to discover as many bugs and errors as possible. Test that covers more functionality and discovers more errors in your software product, therefore considered more successful.
How would you conduct a test: top-down or down-top? What is it? Which one is better?
Down-Top: unit -> interface -> system. Top-Down is a vice versa. You may use both, but down-top allows discovering malfunctioning at earlier phases of development and cheaper to fix than in the case of top-down.
How to develop a test plan? How to develop a test case?
Test plan consists of test cases. Test cases you develop according to requirement and design documents of the unit, system etc. You may be asked what you would do if you are not provided with requirements documents. Then, you start creating your test cases based on functionality of the system. You should mention that this is a bad practice since there is no way to compare that what you got is what you planned to create.