Except in the most formal of writing – which you are not doing if you are getting your tips here – it’s much better to use “I” and “we” and “you.” They engage the reader more. The reader feels like you are talking directly to her. When you say things like, “one expects that,” your reader’s feels like, “Who are you talking about? Who are you talking to?”
People respond much better to an informal approach in writing. When a writer uses “one,” the first thing I think it’s they’re being snooty. I know that’s not true, but it’s a knee-jerk reaction. Once I get past that, I wonder if they’re talking about me.
You may have noticed, I always use 1st and 2nd person when I write. That’s a lot of the reason people like my writing. I get comments like, “I felt like we were just chatting over coffee.” What they’re telling me is they are very relaxed when they read it and are enjoying themselves.
In other words, they are engaged! They want to “listen,” so they keep reading.
Somehow, word got around that writing should be formal in tone. And sometimes it should. But most of the time, keep it casual. Write the way you talk. That’s how people listen. Talk to me, not the thousands of other people who are reading it.