Being honest is important.

Don't pretend to know something or feel something if you aren't.
An experienced interviewer will probe and you will look bad if you aren't honest.

During one of my sister's interviews with PriceWaterHouse for a risk analyst position in the US they asked her a bunch of questions which she totally did not know how to do.

She was laughing in her head that this was horrible cause she didn't know how to answer any of the questions.

However she showed that she was interested to know about it and tried to work at it there and then. Keep in mind that she was stress free as she already got the job she wanted but wanted to go for experience purposes and it was too late to cancel.

She thought she didn't get the job but surprisingly she was one of the few people who did!

It's not about lying or coming out with template answers. I really don't think that will work.

It's about packaging it what you know and bringing the best out of you. Don't reveal your weaknesses but be prepared to come clean if asked or where it's relevant.

I really think being honest to yourself is important. If after all you have to lie to get the job to fit into the job...is this really a job you should be in at all?