Working in software, I get to learn a few rules that are specific to programming that can be easily applied to regular life at the same time. One of the more recent ideas is known as Postel's Law:
Be conservative in what you do; be liberal in what you accept from others.
In programming, this is called the robustness principle and reflects the idea that computer interfaces should be able to accept many different forms of information but always give you information in the same way. Then, just about anyone can send something in to the interface, but you always know what to expect coming back out.
This is a fantastic principle for developing software - your system is flexible, creating a shallow learning curve - but there's also a specific standard for how it works. It's always easier to use something when it "just works," and even more so when it doesn't ever surprise you at the end of the day.
At the same time, though, I find this to be a spectacular example for how a Christian should live their life.
Be conservative in what you do
We have an example to which we should strive to live our lives. I can tell you from personal experience that it is impossible to look on anyone else's actions with perfect clarity and sound judgement. We might look at a man committing a crime and claim to recognize the sin he's partaking in. At the same time, we ignore the fact that we sped on the way to work that morning - also a crime - or kept the extra change mistakenly given by a salesman.
"Why do you look at the speck of sawdust in your brother’s eye and pay no attention to the plank in your own eye? How can you say to your brother, 'Let me take the speck out of your eye,' when all the time there is a plank in your own eye? You hypocrite, first take the plank out of your own eye, and then you will see clearly to remove the speck from your brother’s eye." - Matthew 7:3-5
As Christians, we allegedly know how we should be going about our lives ... but every one of us fails time and again to live up to the standard Christ set for us to follow. Though it is through grace we are saved, we should still live our lives for Him, working each and every day to bring our lives and ambitions more in line with God's will.
Be liberal in what you accept from others
All the same, none of us are qualified to judge anyone outside of the body of Christ. Yes, we should speak into one another's lives as we encourage one another on the path to righteousness. But we cannot and should not expect those outside the Church to live by Christ's example. Setting that as a rule for approaching Jesus sets the bar far too high for anyone to come to salvation.
So while we should not stand for blatant, unrepentant sin within the body of Christ, we should not expect the same from the world around us. Non-Christians will sin. They will kill one another. They will take the Lord's name in vain. They will commit heinous crimes against God. But we shouldn't expect them to do otherwise.
Being liberal in acceptance of the world means only that we recognize the difference between Christians and non-Christians. It means we keep a set of guidelines for those who choose to live by Christ's example and, rather than forcing those rules on an un-Godly world, strive to explain why we choose to live by them.
There are certain standards that Christians hold within the Church that some think should be made the law of the land outside the Church. While I agree with many of these standards and rules, I strongly disagree with making them law. Requiring a non-Christian to live according to a Christian belief system only alienates the non-believer and closes their heart and mind to the message of Christ.
This is why I try always to live my life by a form of the robustness principle: I am conservative in the way I live my own life and the rules by which I conduct my behavior. However, I recognize that others might not understand or agree with my principles, and I will be liberal in my acceptance of their standards and way of life in the secular world.