Hi butterfly1! Journalist here.
It would be hard to give a succint answer to your question. It could be said that the answer is the whole journalism program at college...
But I'll try a possible approach.
It may surprise you, but in journalism the crux of the matter is
very rarely "how do you write". There are a few simple rules to write an article, and you can learn them in an afternoon, so no journalist worth their salt will spend a lot of time fretting about this. The real questions often have to do with "what do you write about", "how do you figure out what is going on", and "why do you write". None of these have a lot to do with the act of writing itself, because, unlike fiction, journalism begins elsewhere and only ends in the written words.
So, how do you write a solid article? Well, you must have a solid article to write. You must be sure you have the correct information, and it must be complete. You must consider the points of view of all involved, even indirectly. You must exercise your ethical judgment about how to approach the subject. Only after you have done the work and made your decisions, you can worry about the wording, the structure, the hooks in the prose. This won't typically take you long. Most of your time will be spent before grabbing the pen.
Now, you talk about people with their own agendas and people who are balanced, and that's a very valid concern. I don't think any of these people are asking themselves how to write a balanced article. They all know how, only some care about it and some don't.
If you have more specific questions, I'll do my best to answer them. Have a nice day!