In my 20+ years of experience in the open assemblies in the United States, typically there are only three explicit prerequisites for preaching:
- Being a Christian
- Being a man
- Having the spiritual gift of teaching
Formal study in a seminary setting is often discouraged, or at the very least looked upon with skepticism. The idea is that any man under guidance of his local assembly, through the indwelling Holy Spirit and regular study of the Bible, is capable of preaching God’s Word to the congregation if he is deemed to posses the spiritual gift of teaching.
This is not to say that assembly preachers never receive any training at all. Typically, training will come from the elders or a mentor in the assemblies who is also a preacher. With a lack of emphasis on formal biblical study, however, it is not unusual for training to start at a very young age. Boys as young as 8, in my experience, have been given the opportunity to give short sermons or testimonies as a way for them to gain experience. So in the assemblies, an 8 year old boy is more eligible to preach than a grown educated woman.
There are leadership workshops and conferences for training as well, like the Shepherding Conference at Greenwood Hills or the Rise Up conferences. There is one assembly Christian college that is seen as acceptable to attend for training (Emmaus Bible College), though any conservative Christian college is grudgingly acceptable.
There are also numerous books from assembly men teaching others how to preach. One favorite is A. P. Gibbs’ classic, The Preacher and His Preaching.
Preaching styles vary from preacher to preacher and even from message to message. There are topical studies, expository preaching, analytical studies, word studies, and various other approaches to scripture and application. Due to the low church nature of Plymouth Brethren (and my gender prohibiting me from being eligible to preach while I was in the movement), there are specific terms for these preaching styles that I’m simply unfamiliar with. The website Voices for Christ hosts probably the largest online database of Plymouth Brethren sermons.
Just as elders are not generally paid staff for the church, preachers are also not salaried and generally there are several men in an assembly who share the burden. Some preachers travel to other assemblies to preach as well, promoting community and ensuring that no one assembly is entirely insular. It’s not unusual for them to be given a love offering from the church.
Most preachers are not typically considered evangelists, however. While most assembly preachers focus on their congregation and a few local assemblies, evangelists are often commissioned from their home assembly to travel and preach regionally or even nationally. While many of them hold full-time secular employment, it’s also not unusual for an evangelist to rely on financial support from a group of assemblies or through the Plymouth Brethren group, Christian Missions in Many Lands.