How are passages vetted for inclusion in officially sanctioned liturgical readings? Inspired by this question, I am very interested to find out how specific passages are "vetted" for inclusion into official church liturgical use?

I realize this process may be different for Roman Catholic, Anglican, Episcopalian, etc traditions. Not relevant to this question would be any denomination/tradition that just reads from the Bible based on a cycle (eg, one chapter per Sunday in consecutive order), or on the pastor's volition.
I am a member of the United Methodist Church, so my answer will be from that perspective.

In the United Methodist Church, preachers preach from the Lectionary.

According to Wikipedia:


  The Revised Common Lectionary was the product of a collaboration between the North American Consultation on Common Texts (CCT) and the International English Language Liturgical Consultation (ELLC). After a nine-year trial period, it was publicly released in 1994. The CCT membership includes the United States Conference of Catholic Bishops and the Canadian Conference of Catholic Bishops as well as many traditional "mainline" or "liturgically-based" American and Canadian Protestant denominations such as Lutheran, North American Anglican (Episcopalian), Presbyterian, and more loosely Methodist and/or Seventh Day Adventist. The CCT thereby represents the majority of American and Canadian Christians and has been widely adopted in Great Britain.


The Consultation on Common Texts explains the process by which the current Revised Common Lectionary came about in this PDF file.  It appears to be a process of collaboration and suggestions from the various denominations.

The Revised Common Lectionary appears to be a product of the majority of American Christian faiths.

For those not familiar with the Lectionary, the book contains 4 Bible readings for each Sunday for a 3 year cycle.  The church year starts with the first Sunday of Advent, which this year happens to be Sunday, November 27, 2011.  This new year is Year B, or the 2nd year of the 3 year cycle.

A preacher can use any or all of the 4 Bible readings in a worship service, and still be considered as preaching from the Lectionary.