Don't lie

Lying can really cost candidates. If you get caught out in a flat out lie, not only will it almost certainly sink your chances with the employer you lied to, it could become a real point of gossip and bad reputation. 

As a case in point: A friend of mine on a hiring committee received an email from the adviser of someone they had flown out. The adviser told him that he had been in touch with another school the candidate had flown out to,  Apparently, the candidate had falsely claimed he had a Revise and Resubmit from a very good journal that significantly improved his CV. The adviser was so concerned that his student would get a job on false pretenses that he felt obliged to let all prospective employers know. Although the candidate had not actually told the same lie to my friend, the story set off warning bells, and he was not hired. This is obviously an extreme case, but it illustrates the point.

The far more common case of "lying" is insincere flattery. I teach at an unranked department. It's a nice place to work, but we know who we are. Every now and then we will interview a candidate who says something along the lines of "I want to work at your department because it is one of the best in the world." It just sounds silly. It's good to seem enthusiastic about a job, but do it in a reasonably honest way. What I recommend is that you try to get as excited as possible about each job before each interview or flyout. Do a little research and thinking about what makes the job good. Every job has some appeal, just find it.  Research intensive jobs are great for advancing your career and research agenda. Teaching focused jobs are great if you like teaching and usually involve shorter hours and less stress. Urban areas are vibrant and fun places to live. Rural areas offer lower costs of living and an opportunity to participate in outdoor hobbies.

Just because you have to tell the truth, doesn't mean you have to the whole truth. If the truth would not be in your favor, you can withhold it to a reasonable extent. For example, you can say "I am excited about the prospect of working at your school" without adding "but not as much as I am excited about a lot of other places". 

Just be careful about making your answers sound too cagey, it comes across as odd. There are a number of somewhat common sticky questions like "where else are you interviewing?", "where do we rank for you?", and "how likely would you be to accept an offer from us?". They probably shouldn't be asked but they often are and they tend to tie candidates up into knots. Ideally, you sound candid, straightforward, and positive, remain honest, and don't reveal anything you don't want to reveal. It is a tricky tightrope to walk, and you might want to plan ahead of time how to do it.

 And of course if you get asked an inappropriate question about something like you sexuality or marital status, feel free to politely but firmly refuse to answer. Don't get indignant or make a big scene. Most likely the person asking you did it out of ignorance or carelessness and you both would be best off quietly moving on.