"Can you tell me about the 'Good News'?" "Come on, tell me. I've noticed your 'light shining', there's something different about you, you seem to have some sort of inner joy that I'm interested in."
This generally isn't going to happen, you're going to have to approach people and start the conversation. Are you prepared to give a reason for the hope within you (1 Pet 3:15)? How do you, as a Christian, share your faith (as you are commanded to in the Great Commission)?
There are those who would say that the Law is not applicable to us today. They might claim that it was only for the Jewish people, or they may say that it no longer applies since Jesus came with grace, as they cite "legalism" or "works-righteousness."
While it is true that no one is saved by the Law (Rom 3:20), the Law of God still has a prominent place in Christianity. It is based on His very nature, and is the standard He gives mankind to live by (Rom 8:7-8).
Scripture tells us that the Law is good if used lawfully (1 Tim 1:8), bringing knowledge of sin (Rom 7:7), and it acts as a tutor to lead people to Christ (Gal 3:24). Psalm 19:7 tells us that the Law of the Lord is perfect, converting the soul. Why have we forsaken the Law in the last 200 years or so (2 Tim 4:3-4)?
The Ten Commandments are all restated in the NT, except for the fourth one, which is opened up to worship on any day of the week, no longer limiting us to the Sabbath day (which is Saturday, btw).
Early believers started meeting on the first day of the week (Sunday), because that was the day that Jesus rose from the dead.
It is impossible to witness to someone Biblically without using the Law, you just need to learn how to use it properly, in an inoffensive way, by asking questions to allow a person to judge themselves by God's standard. This doesn't mean that no one will be offended - the cross is foolishness to those who are perishing (1 Cor 1:18), and some simply refuse to give up their sin.
But in order for the Gospel to make sense, people must understand their NEED for a Savior. Otherwise, why would they come? They consider themselves to be good people (Prov 20:6), looking around and seeing all the others that are far worse than they are - just watch the evening news - right?
We justify our own actions, and condemn the sins of others, which is what makes men such hypocrites. Hypocricy is not limited to church members, it's ramant throughout all mankind, it is a part of our sinful human nature.
But the question remains, are we good by God's standard? And the million dollar question: "Are we good enough to get into heaven?" The Bible says that there are none found good, not one, that we are all sinful and fall short of God's standard. But that's too general, God actually gives us specifics, let's look at His Law, summed up in outline form in the Ten Commandments (Exodus 20:1-17). Have you kept them? Most people don't even know them, even though they are written on our heart (Rom 2:15).
We know it's wrong to murder (6th), to lie (9th), and steal (8th), don't we? We understand that adultery (7th) is wrong, that we should not covet other people's belongings (10th) and that we should not make idols for ourselves (2nd), right? We can comprehend the fact that we should honor our parents (5th), keep God first in our lives (1st), and not blaspheme His name (3rd). We know that God has given us every blessing we have, even our very life. Is it too much to ask for one day out of seven to give back in thanks and worship (4th), no longer limited to a Sabbath day, but any day of the week?
Examine yourselves to see if you're in the faith (2 Cor 13:5). Then go out and share the Good News with others, not waiting for them to come to you, but take the inititive (Mark 16:15), you have been commissioned by God to witness to others (Acts 10:42).
Don't be a hypocrite, crying, "judge not!" (John 7:24) while you yourself judge aperson as saved so that you can remain silent (Ezekiel 33:8-9). It's still judging, but a much more dangerous way of doing so. By simply assuming that a person is saved without digging a little deeper with questions so they can examine themselves by the standard of God could leave them in a false sense of security (Prov 16:25), only to be revealed when it is too late (Matt 7:21-23).
You might as well just tell them to go to hell, because that's what you're saying by your silence (Acts 4:12).
"Have you no wish for others to be saved? Then you're not saved yourself, be sure of that!" - Charles Spurgeon