Some useful tips for a successful interview at UPSC are:

1. To have a positive body language
2. To have a good personal turnout and ensuring the right posture
3. To answer questions clearly and confidently
4. Try to remain calm and composed even when faced with provocative questions
5. Try not getting into long winded explanations and answer to the point.

Things To Be Avoided at the UPSC Interview

• Avoid the expression, 'I am sorry.'
• Avoid conversational cliches, like: 'as you know', 'that's correct', 'of course', 'indeed', 'obviously', etc.
• Avoid technical jargon. However, if a member continues to probe you in any technical field, you can use technical expressions.
• Maintain a cheerful disposition. Now and then you can appear serious; but most of the time keep smiling or look cheerful and composed. One caution here: if the board laughs, you should only smile. It is only when you maintain some amount of distance that the board begins to wonder about the depth of your personality.
• Do not give long introductions. Come straight to the heart of the matter.
• Show human concern whenever possible in your answers.
• You should be logically consistent and analyse things rationally while talking. You are supposed to defend what you say, but with due respect to the views of the board. Stop trying to defend an answer if it becomes difficult to do so logically and fairly.
• Do not make hasty or sweeping generalisations.

According to UPSC report, it has been observed that from 1979 onwards, 90 percent of the candidates who qualify for interview hover around the minimal percentage of 55 percent that is prescribed for the test. However to be assured of a Class I service, one has to generally obtain about 58 percent marks. It has been noticed that only those, securing 60 percent and above are sure of getting a service of their own choice. The figures clearly reveal that the marks in the interview test play a determining role in final selection of candidates.

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Types of questions asked at the UPSC interview.

• Relating to your name. Any famous personality who has a similar or same name or surname.
• Your career choice. Why you want to opt for the civilservices.
• Your Hobbies. Why you pursue such a hobby or questions related to your hobby. So reasearch well on your hobby.
• Hot topics of recent days like the Bird Flu and Tamiflu, Office of Profit, Sahara airlines deal and the growing airlines,Terror attacks in India, India US Nuclear deal, Commonwealth games, Saurav Ganguly etc.Keep reading and watching the news. If the recent headlines have something to do with your subject then specially revise those portions. For example if you are a veterinary doctor, Bird flu may go on to other animal diseases that can infect men. If you are an MBBS, then you might be asked about human to human spread of epidemics or any other epidemics and precautions etc. You may even be asked about the influence of MNC or drug manufacturers responsible for the spread of fear etc. If you are from an economy background, the same topic will veer towards the economic implications of the Bird flu.
• How you are going to use your specific knowledge(like if you are a doctor, lawyer, engineer etc) in the services.
• Situational questions. Like If you were the collector/SP of Varanasi, what would you do after the Bomb Blast?
• Choice of services. The order of your choice of services can raise questions too.
• About your institution and related.If you have studies at IIM you may be asked about the rising salaries, if from IGNOU then even about Indira Gandhi and so on.
• From your form. You must go through the form you have filled because most questions will arise from there. If you have changed subjects, mentioned anything out of the way, watch out for questions on them. Interviewers take cue from the form you have filled.

Some actual questions asked of UPSC candidates.

• Don't you think you can serve your country better by remaining a doctor and treating poor patients? Why do you want to be a civil servant?" 
  It would be best to answer this question very practically rather than emotionally saying you want to serve the country, because even a doctor serves the people. A doctor from Kerala was asked this Question and her reply was - "Because I want to treat the primary malady that afflicts our country, that creates so many poor in India. As a doctor I can treat only secondary maladies." She even came up with exact statistics and suggestions on a rubber plantation for poverty alleviation indicating that she had spent considerable time and thoughts on her future plans. She was awarded a score of 85 per cent.
• "What are the problems faced by wheat cultivators in your state?" an M.Sc. (Agriculture) student from Palanpur was once asked. "The problem is not so much to do with agronomy but with the lack of a seed bank in Palanpur," came the reply and the candidate walked away with an 80 per cent score.
• "Is there a law in physics, which is relevant to administration?" a law graduate was prompted. "Yes. Newton's third law of motion: for every action there is an equal and opposite reaction." He scored a cool 80 per cent.

  The above questions can give you an idea of how relevant questions are asked from your subjects even as they are not directly from the syllabus.