(1) While it is often the case that writers of theological works desire to express themselves in long, flowery sentences replete with extraneous modifiers and prepositional phrases, thereby demonstrating to their readers the depth and profundity of their grasp of the topic, it is, in fact, far preferable to write simply and directly, so as to facilitate greater comprehension on the part of those who will read these lessons not for intellectual stimulation but to prepare an acceptable Sunday school lesson for an audience primarily composed of Christian laypeople.
(2) Comprehension is often hindered by overuse of the passive voice. This construction is accepted by linguists and grammarians as grammatically correct. Even so, it should be avoided when possible. Your writing should not be allowed to be encumbered by the false notion that readability is enhanced by the use of the passive.
(3) Adverbs are very nearly useless. Although they can sometimes be quite helpful, it is rather easy for them to quickly accumulate until they unexpectedly take over what might have been a fairly clearly written sentence. You should probably avoid them most of the time.
(4) The salvific benefits of hesychastic contemplation of the eschatological ramifications of the parousia notwithstanding, most readers prefer a minimum of technical jargon.
(5) Mutatis mutandis, the same is true for gratuitous foreign phrases.
(6) Utilize locutions of primarily Anglo-Saxon derivation in lieu of French or Latin equivalents.
(7) Remember that readers—and even editors—may not understand cultural references that are second nature to you. Provide a little bit of context or you’ll end up sounding like the Tamarians at El-Adrel!
(8) Never use a big word when a diminutive one will suffice.