I wanted to say I have problems sharing the gospel with people, mainly because I'm not comfortable talking to people. Yes I love reading God's word and debating with you on His Word (not really), but I'm not good at sharing the Word with others. The only thing I know I can do is to be an example. Of course I practice God and Jesus' words. I'm not a shame to seek advice and help. One thing I know God hates is a proud heart, but the humble heart he loves.
I was talking to one of my sister (she's three times my age) and she was correcting me on how I need to be careful in how to share the Gospel in that when I share the Gospel to not let people feel inferior to me, not to point out their sin, basically be careful not to be self-righteous as if I was better than others because I was in Jesus or I don't do a certain sin. So I wanted to know if you can give me some advice on how to share the Gospel, and what to be careful about in presenting the Gospel to others.
The topic is so broad that it is hard to decide where to begin. Some people will not be as talented as others in teaching. We are all to do our best, but some will naturally be better at teaching that others. But that is fine because we all have our own talents (Romans 12:4-8).
Teaching others, though, comes with extra burdens. "My brethren, let not many of you become teachers, knowing that we shall receive a stricter judgment" (James 3:1). When you teach, you are responsible not only for your own soul, but you make yourself responsible for the soul of another. Thus the accuracy of what you teach is critical because God will hold you accountable if you lead someone astray.
In some ways, your friend is right. "But avoid foolish and ignorant disputes, knowing that they generate strife. And a servant of the Lord must not quarrel but be gentle to all, able to teach, patient, in humility correcting those who are in opposition, if God perhaps will grant them repentance, so that they may know the truth, and that they may come to their senses and escape the snare of the devil, having been taken captive by him to do his will" (II Timothy 2:23-26).
But she is also wrong. You can't help a person out of sin if you don't point out that they are in sin. "Son of man, I have made you a watchman for the house of Israel; therefore hear a word from My mouth, and give them warning from Me: When I say to the wicked, 'You shall surely die,' and you give him no warning, nor speak to warn the wicked from his wicked way, to save his life, that same wicked man shall die in his iniquity; but his blood I will require at your hand. Yet, if you warn the wicked, and he does not turn from his wickedness, nor from his wicked way, he shall die in his iniquity; but you have delivered your soul. Again, when a righteous man turns from his righteousness and commits iniquity, and I lay a stumbling block before him, he shall die; because you did not give him warning, he shall die in his sin, and his righteousness which he has done shall not be remembered; but his blood I will require at your hand. Nevertheless if you warn the righteous man that the righteous should not sin, and he does not sin, he shall surely live because he took warning; also you will have delivered your soul" (Ezekiel 3:17-21).
Different people will require different methods to reach them with the truth. "And on some have compassion, making a distinction; but others save with fear, pulling them out of the fire, hating even the garment defiled by the flesh" (Jude 22-23). A good teacher knows when to vary his approach to make the best impact.
There is a study on this site on the topic of how to teach others. See Keys to Understanding.