Whether you are writing a magazine article, composing a press release, or editing the content on your website, the end goal is always the same - to influence the thinking, and probably actions, of other human beings. To do that, your writing must instill confidence in a mind that is inclined to doubt you.
Here are a few tips on keeping the reader on your side.
Keep your word count under control. Keep it simple and don't say any more than necessary; when you write, limit your word count from the start. Never spend 1000 words covering ground that could have been covered in 200 words - the extra material looks exactly like the useless filler it is.
Don't hedge. At all. Sometimes a writer is worried about offending the reader, and so either avoids making direct statements or pads the statements with language designed to soften the blow. Don't hedge - be bold and direct, and let the reader be offended. You can't make everyone happy, and you'll look like a fool if you try.
Be on the lookout for language - phrases like "taken as a whole" and words like "basically" - which doesn't contribute anything towards supporting a direct claim. Weed out the hedging and get back to simple noun-and-verb statements.
Use active verb tense - avoid passive tense at all costs. Active verbs describe the subject committing an action and influencing its environment ("Jim drove his car"), while passive verb clauses dislocate the subject so that it becomes secondary to the predicate clause ("The car was driven by Jim"). Typically any verb clause in the "to be" family ("has been", "is being", etc.) is a passive clause.
Don't use passive verbs; they express impersonal events rather than committed actions, and they create distance with the reader. They avoid a sense of personal accountability. Active verbs draw the reader closer and fix responsibility.
Maintain an optimistic, positive tone. Politicians everywhere know that good news wins elections. Limit your use of negative statements as much as possible, and focus on the positive.
Give your reader a sense of hope rather than apathy.
Even if circumstances require that you deliver bad news, do so with optimism: there are problems, but we are solving them. Don't deny or avoid obvious unpleasant truths - if your reader knows about them already, your avoidances will only damage your credibility - but keep control over your tone.
Promoting a consistently optimistic image
to your readers goes a long way towards generating confidence, or at least benefit of the doubt.
Structure your writing carefully. Carefully plan out what you intend to write, and then follow the plan.
Don't make it up as you go along.
Don't wander and don't be indirect - organize your message carefully, to say the most in the least words possible. Demonstrate that you are in control of your communications, and worthy of reader confidence.