These are all part of a coherent whole and do not have to be created or decided upon in order. I often don't do any of these in the order listed:
1. Name/pronouns/nicknames
2. Physical attributes
3. Mental/Personality attributes
4. Background
5. Your Intent
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Visualizing your character is going to radically improve how you write about them. Not that you have to give exact numbers, but how tall are they, what size, what color hair, do they have hair even? Are they even human? .
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The best part about this portion is that you do not have to reveal it to your readers if you don't want to. If you're following in the style of the Romantics and spending two pages describing a character's left hand, more power to you, but I am not that kind of writer. In fact, I'm the exact opposite. My character descriptions are often sparse if they ever happen.
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I like to leave negative space for the reader. That way, when I do give a detail about someone's appearance, it sticks out as a cornerstone for them to build their own interpretation. .
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However, with that being said, I concretely visualize them when I write about them. I'm not a stranger to making bulleted lists of specifics about their appearance to help me do so. I'm also a very visual person, so I often imagine my prose happening like a movie. A character's physicality speaks volumes (no pun intended). If you can see them in your mind's eye, you can give them proper actions, stage them in a room, get a feeling for how they use their limbs or their facial expressions.