Our culture, including our churches, is reticent to add more meetings and events to our schedules. One of the best ways to help a church begin praying for missions is by integrating it into situations where people are already praying. For example:
Children's Sunday School classes are a great place to integrate prayer for missions. Provide teachers with a short, simple prayer point, written in kid-friendly ways, such as the THUMB prayer cards.
Ask what adult small groups or Sunday School classes might be willing to pray for a nation or a missionary once a month or quarter to start.
Ask your pastor if he might be willing to integrate missions into his pastoral prayer with some frequency.
Propempo has promoted the idea of "Missions Advocates" for adult Sunday School classes, Bible study groups, each small group of a small group ministry, etc. A search for "missions advocates" on Propempo's site will yield several articles and resources. One of the key responsibilities of a Missions Advocate is to keep informed and remind people in their particular context to pray for the missionary or ministry for whom they are advocating.
Pastors, teachers and small group leaders are busy people who are challeneged to prepare for their groups. You will need to regularly provide leaders with relevant and timely missions prayer requests.
Hopefully consistent prayer opportunities will help a group emerge that wants specifically to pray for missions. When a core group of people is prepared to pray together consistently, define the prayer purpose of the group and determine a regular time to meet. Pray not only for missionaries, but also the unreached people among whom they work. Integrate worship, visual aids (such as maps) and video clips that will foster engaged prayer.