This is a very good question, @Koberheu. It’s also a rather difficult one to answer, (at least for me). My own personal experience is that I learn the best through stories and allegories. I’m sure that’s common. Jesus spoke in parables to convey truth for two reasons.
One is that people can grasp truth easier when it’s related to every day living. For example, Jesus used agricultural terms a lot, because he addressed a lot of people who were farmers. Jesus understood his audience and spoke to them on their level.
The second reason was two fold. He purposely told parables that we’re difficult to understand at first blush so people were forced to think deeper and in different ways to discover the truth. In doing that the truth was embedded into their minds and they retained it better. I had an instructor who taught that way. The more you had to research and think on the information, the more information you retained.
The second reason was to sort of “weed out” those who were not really interested in learning the truth. As Jesus taught and performed miracles, he started to attract more and more people. I’m sure you remember the story of Jesus feeding a crowd of 5,000 people with 5 loaves of bread and 2 fish. Thousands of people were attracted to him. But, Jesus knew that most of them only came out to see the “show”. They were wanting to be entertained. They weren’t interested in knowing the truth. So Jesus taught using an allegory that sounded like cannabolism. He told them that in order to have eternal life, they had to eat his flesh and drink his blood. Most people thought he had gone insane and left. The ones that were left were the ones who were totally committed to learning the truth.
In regards to how to get started, I would sit down and write out my testimony. It helps to have down on paper. That way, you can remember important details and it helps you get it straight in your head. Also, you can read through and edit it to pick out words and phrases that sound like “Christianeze”; terms like “born again”. Then you can work on breaking it down into secular terms. I’m sure there are stories in your life experience that people can relate to.
Another thing you can do is read Christian authors who are experts in story telling. Some of my favorites are C.S. Lewis, with his Narnia series, George MacDonald has several, too. Some modern authors that I recommend are Max Lucado, Ted Dekkard, and Frank Peretti. I have learned a lot from them.
I hope this helps. I pray the Lord will help you and give you ideas that would open up peoples minds to His truth. The Holy Spirit is the power behind our words to penetrate people’s hearts.