Over my years on Wikipedia, I have developed a series of guidelines in addition to standard grammar for writing what I believe are high quality, encyclopedic articles. I believe sharing them might be beneficial for other editors, but these are just my opinions.
Words to avoid
- that - extremely overused and usually unnecessary filler. If it can't be removed or replaced with which, the sentence may need to be rearranged. I find this helps add variety to sentence structure.
- himself or herself - pretty much always added for emphasis, pretty much always redundant. When used correctly, it should follow a verb ("He hurt himself."), not a noun ("It was David himself who did it." or "David did it himself.").
- revealed in the context of an announcement - overused and typically paired with that and name dropping ("Source revealed that ..."). Unless the revelation is truly dramatic ("His mistress revealed a secret love child"), just remove the phrase and tell the reader what happened.
- subjective adjectives - fluff that typically carry connotations beyond the tone and neutral point of view of an encyclopedia. If they can be sourced, attribute the description inline so it's clear that a reporter, not Wikipedia, called the woman "enormous". Limiting the use of adjectives to when they're really needed will make them stand out more. This specifically excepts objective adjectives, like color or comparisons.
- adverbs - virtually never needed. Let the verb speak for itself. If you think it's important to say "He ran quickly", show why by saying "He ran quick enough to..." If you can't complete this sentence in this format, then you don't need the adverb.
- very - technically covered by bullet point above, but this one's a special case because it's the most common and the least needed. It's also vague. Don't say someone "was very late"; either be specific and say she "was two hours late" or leave it at "was late".
Phrases to avoid
- the fact that - wordy and useless. Cut this out and get to the point.