Set an example, walk the walk, and talk the talk, if there is a conflict between the two, people will not listen to you. "What you do screams ever so loudly in my ears, I cannot hear what you say." (Ralph Waldo Emerson) Care about your students with a genuine concern. Ask them how you can be of service to them, "What can I do to help?". People do not care how much you know till they know how much you care. People are loved into the Kingdom of God, not talked into it. Words are important, but they mean nothing without God's love. I Corinthians 13.
When we start our classes, we have a short "meditation" time. I always explain to the students the Biblical form and meaning, "Think about these things, (Selah)," not empty your mind and let anything wander on in. Biblical meditation is to focus on God and the abilities He has bestowed upon you, then develop them to their (and yours) fullest capacities.
I openly talk about my faith when the time is appropriate. Never try to force sharing your faith because you feel insecure. "Well, gee, here it is another week of class and I haven't said anything about the Lord." Indeed you have, if you are letting the example you set before the class speak for itself. Be joyful and enthusiastic about your Martial Arts. People will start asking you how it is you're always so happy. Sounds like a sharing opportunity to me.
Always go the extra mile. I am a second degree black belt at my school, and will shortly earn my black belt in Jujitsu, I still help clean the bathrooms, run the vacuum cleaner, fix broken things around the school. If someone needs help I will try to help, or find someone who can. Remember, when you announce to others that you are a Christian, they are watching.
Students are coming to our schools to learn martial arts, we on the other hand know they need Jesus. Ministry always flows through relationships, get to know your students on a personal level, but always use wisdom in doing so. Pray for them.
If you can, start a Bible study at a time that
does not conflict with class time. Teach Bible basics, and open the discussion
to those who have questions about God and who Jesus is. Invite people to
church with you. If the school owner does not object, put out flyers announcing
special events at your church. You will notice most of what I do, and have
said here has a lot to do with "being an example, letting your light so
shine before men," and not just a "hot blast of Gospel preaching." This
is the majority of what and how I share the Gospel with others as an instructor,
and a student.