Desiring God had a really good post recently entitled 30 Ways to Awaken Your Congregation for the Cause of Global Engagement.
Points #7, #8, #9 of the blogpost ring true with me these days so I wanted to see them.
Incorporate world-aware prayers into your worship services, and encourage the formation of an accessible, missions-focused prayer group in the church (perhaps based on the book Operation World).
Visit your missionaries. Have people help them move, and regularly send teams to minister to your missionaries and potentially aid in the work. Missionaries are usually more inclined to share needs with a visiting church member than their field supervisor.
Commission individuals and teams when they go, and set up an avenue for them to report on their work to the rest of the church.
Check out the entire post here.