Remember always to focus on what makes you an ideal candidate. Do not enumerate reasons why another candidate is a poor one: you might be perceived as someone who is bearing a grudge. Think about the job vacancy and choose everything from your experience that makes you an appropriate candidate. This is the advice of the business2community.com website.
Focus on your assets
Do not try to guess what the qualities and skills of your competitors for the position are. Show the potential employer where your strengths lie and explain how your experience is relevant. You have to tell them why they should hire you. Your experience, combined with three important skills, should be what will set you apart. Forget about the other candidates because you don’t know them. Trying to demonstrate your superiority in comparison with them is not a good idea since it is quite likely they also will have some interesting experience.
When to compare yourself directly with others
Even if you do know some of the candidates, never badmouth them, even if it might be tempting. You should focus on what makes you a professional; badmouthing, however, would rather harm both you and your image. So forget about any personal antipathies. Comparing yourself with another candidate is in order only if you are being interviewed for an internal role or a promotion. But even then avoid commenting on personality traits and previous incidents. Instead, you should be focused on quantifiable facts, over which there cannot be any dispute. Talk about how many years' experience you have had in a similar role and the qualifications which, in contrast to the others, you have obtained. You should speak solely about your own personality traits, not about anyone else's.
Know as much as possible about the position
Every answer you give in response to questions must be relevant. Do not talk about overly personal matters, especially if your hobbies are not relevant to the job you are interested in. But if mentioning one of your hobbies could demonstrate some of your skills or abilities, then of course do say something.
-jk-