Every person who I have taught and helped prepare for baptism during my mission has come because a member of the Church of Jesus Christ of Latter-day Saints had the courage to share what they knew to be true. Every time. And from that, I have a huge testimony of the power of member missionary work.
- Pray for missionary experiences. Pray for the missionaries worldwide, and in your own ward/branch/stake.
- Offer the missionaries rides, if needed.
- Invite the missionaries over for dinner and, if possible, have a non-member or less-active member present. Even if you don't have a non-member or less-active member over, we love getting to know the active families. There is such peace in members' homes that is sometimes hard to come by elsewhere.
- Prepare to share the gospel with others. Think of some questions that friends have asked you about the gospel, and prepare simple one or two sentence answers to them. Then, when you are eventually asked about that topic, you don't have to sift through the deep doctrine files in your mind to find the simple answer they're looking for.
- Have some pass-along cards or Book of Mormons in your car/purse/desk, etc., ready to share when the Spirit prompts you do.
- Be familiar with various church media that you can share with others. Check out the pages and videos on Mormon.org, make your own Mormon.org profile, and check out the Lds.org Media Library. You can easily e-mail/message these videos to your friends, or post them on your facebook wall. You can get DVD copies of some of the videos from the missionaries, like "Finding Faith in Christ" or "Joy to the World" (the first is about Christ, the second is Christmas-specific, but both would make great gifts).
- Read the Ensign/New Era/and Friend magazines. Sometimes, just by reading something, I'll get an idea of who I can share it with, or who needs a visit this week. You can easily print the article off from the website and drop it by / mail it to them. I love sweet, simple acts of service like that.
- Invite family friends over for Family Home Evening. Even being in your home can help them feel that special spirit that the gospel brings.
Some excellent talks on the subject:
"Be Thou an Example of the Believers," by Elder Russell M. Nelson
"The Member Missionary Effect," by Don L. Searle
"Be a Missionary All Your Life," by Elder Quentin L. Cook
"How Great Shall Be Your Joy," by President Henry B. Eyring
"Letting Go of My Fear," by Gilda Hughes Christensen