How to prepare a coding paper test which the job involves C++, Java, C#?

Yes, I have an idea: if you don't know this kind of work right now, don't apply for a job.

Seriously, preparing to interviews it totally useless. You need to focus on your knowledge and skills, nothing else. Prepare yourself for work, as if you are already hired, never for interviews. You never know what they ask. And, after all, you don't really want to get someone else's position, you want to work at something you can really do well.

Of course, some experience is useful, but this is more psychology, behavior, etc. You cannot prepare technical answers, train in solving test problems, or something like that. You can get this experience after several interviews, better prepare yourself that you won't immediately get your job. You really need to learn technology and sharpen your skills.

Want one simple secret? Imagine you are already hired and only discuss the detail of your employment. There is nothing bad in this, no cheating; it's just one of the way to get right attitude. This way, you can have more relaxed view on your chances for the position and can focus more on the problems of your prospective employers. This is what these people would really expect (if they are reasonable people): you can understand what this company or team really needs and offer them your help, some possibilities you really have as a knowledgeable developer. So first of all, you need to be such a developer, not a test passer. :-)

—SA