Is fourth precept personal and depends on the individual?

I find it very hard to get a clear understanding what is considered a breach of this precept and what is not. Different perspective offers different answer. For example: Some people considered social niceties such as "I'm fine" as an answer to "How are you?" is not lying (when someone is not fine). Some people do not make such exceptions, when you say something untrue, that means you are lying. Receiving foods and say "Thank you, it's delicious" is a lie since the food is not eaten yet. Some people said that is not lying but an expression of gratitude. One person views others as justifying lying. The other person views others as being (too) dogmatic, which is not the core of Buddhist teaching. How can we have a clear cut understanding about this particular precept therefore put them into practice? To what extent it can be considered misrepresenting untruth?