The church makes a mistake if its gatherings fault to one of two extremes. The most common mistake is one we are all familiar with: the traditional church's planned gathering. We've all seen the limitations upon edification that come from a scripted worship service. Most of the body is muted while a few people do almost all the talking, etc. This planning has good intentions and often leads to a nice ceremony, but it stifles the body.
Another mistake is the opposite extreme. This usually occurs in simple church or house church gatherings. The mistake is one of no preparation. When this occurs, everyone shows up looking for the Holy Spirit to lead, but little edification happens because no one is prepared to add anything. This type of extreme spontaneity can lead to people saying things they wouldn't normally say in order to fill a gap in the silence. I'm not speaking about a legitimate form of prophecy, but rather speaking words that simply fill a void.
Both extremes (planned services and no-preparation meetings) fail to follow what we read in I Corinthians 14:26, "What then, brothers? When you come together, each one has a hymn, a lesson, a revelation, a tongue, or an interpretation. Let all things be done for building up." The scripted service violates the idea of "each one." The no-preparation meeting violates the idea of "having."
Paul's intent is that the body come together having prepared something to add. This something may be a specific teaching, hymn, or word of exhortation. It may also be an attitude of readiness to add a word of prophecy, a prayer, or a tongue. We see that Paul believes that at least some form of preparation is important in leading to mutual edification.
As we ponder our church gatherings, we should ask ourselves whether or not we are preparing anything. Maybe it is a passage of scripture to read. Maybe it is a short testimony. Maybe it is a word of challenge. Maybe it is a lesson. Maybe it is encouragement. Maybe it is a specific song.
We must be prepared, but also let us remember that we may not add what we have prepared if the Spirit tells us not to. For example, if it turns out that five people have prepared teachings, the best thing for the body may be for one or two of those people to refrain from teaching that day. This act of humility, possibly only known by God, may be a benefit to the body.
In the end the Spirit must lead the gatherings. He tends to lead through using what we have prepared. Let's be prepared.