Don't you think taking interviews of a desired candidate makes him very much aware and also prepared?

Yes a brief interview can probably only tell you so much about a candidate and some professionals are much more skilled at presenting themselves than others in an interview scenario. 
Some companies use psychometric tests (such as those on ww.bayt.com) and skills tests and online questionnaires (also available on bayt.com) to further screen and rank candidates and others incorporate panel inteviews and group assessment centres into the talent screening process. 
A lot has been written about the merits of various types of interviews but at the same time a lot of literature exists on leading jobsites and elsewhere to prepare candidates for any interview situation. 
The majority of companies will insist on various interviews with different team members before a hiring decision is made and most leading HR departments today have very coherent hiring manuals in place that detail their company's interview guidelines and hiring process so all involved in the hiring process are trained and prepared to make the most informed and optimal decision. 
In any case the probation period exists to ensure that hiring decisions translate into an optimal fit between candidate and company and that all parties are happy with the recruitment match.

Its normal that some candidates are very smart can be prepared to the interwier very good.
But our task as hr managers is to be some steps faster and futher then candidate.
There are non standart metrics which can allow yourself to check employee personality, and for sure would be good to organise some tests to check professionalsm.
From my practice its good to ask very concrete questions, examples to see employees behaviour in different situations, even real practice situations from working life.
But in any case we have Probation Period and its normal that sometimes employees dont pass it successfully.
Usually I analise such cases for the future.
And hr position should be independent like a partner, if yop see some negative aspects or risks for the company in potential candidates its good to say about this to Employers.
Then they have to make a decision to hire or not this candidate, in this case he will take responsibility for the candidate being in the company.

It migh be true that some candidates are too much prepared; yet you should know that the aim of the interview is not to trick the candidates; its aim to identify their competency. If they are so much prepared as you know and predict your questions this mean that they are competent enough to know what the organisation is looking for and they are very good in presenting it; this in return predict that s/he might be good candidate.

Finally, the recruiter should be able to identify the candidate competency even if he is very prepared and this through indirect questions and uncommonly used phrases.

Recruiting is expensive! In time, money, hope, energy, trust and credibility ...

But how to capture the right talent, the one who will flourish, grow and contribute to the performance of the organization ?... that is why it is urgent to ask the right questions, to use the right tools, to choose the right ones indicators, and put in place the right strategy: because it is true that choosing a candidate, according to an interview is not a risk-free operation.is for that, I think this operation must be done in two phases, 1-Target the profile that is needed .2- Pass to a trial period, to maintain the candidate, while keeping a queue waiting for a replacement candidate potentially suitable for the position.

A candidate shall be well prepared and must know about the background of the organisation he or she has applied to. 

In this case it is necessary to have witnesses if not it is necessary to filmed it then secretly filed a complaint based on dismissal pieces and prison because corruption is a phenomenon dangerous for society therefore it is necessary to lose

#1 of being rejected by the company on the early level of recruiting is because the candidates did not do this small effort to get the knowledge about company, position and expectations. Once you are invited for an interview at least visit the webpage and check company profiles. It works... Esecially while answering the question: "why would you like to join us?" In that moment we can shine by our knowledge that the comany - for example - is listed as a top500!

 

The real question from my personal view Is, why we do give a chance to the candidate to let him get ready for the interview?  especially for those who are a new graduates 

 

I do not see that, this is a mistake at all, If I have the authority, I will add this point as one of the interview requirements. 

Correct hiring is half work done. The forbes 100 companies portray that they take multiple stages of interview to identify the candidate. Also it should be noted that knowledge is not the only key for any job, the aptitude, problem solving, team playing skills are at times ignored and thus company suffers due to lack of these qualities. The proper time to make them prepare and then evaluating them for various key elements is the key. It is an approach which is win-win for both parties and essential for success for both. 

There are many who are not good in facing terminology specific interviews but good at handling their responsibilities. Therefore, the situational questions could be the right way for such lot. The interview should be mix of all and candidates must be encouraged to speak more to feel comfortable. This will help identifying the right person. In house permotion should be simply based on past performance where candidates are given additional responsibilities from time to time. Each time such performances should be recorded in personal file for reference.