Word order for adverbs in professional prose

Question

I've been editing for my girlfriend, a non-native speaker, recently, and she asked me an interesting question, which we have modified to the following two questions:

1. Which sounds more natural?
2. Which reads better?

Here are the options in question:

1. First, we focus on the thing.
2. We first focus on the thing.
3. We focus, first, on the thing.

We are both Ph.D. students in mathematics, so we are, as a rule, befuddled by non-quantifiable quandaries.

Answer 1

They all sound natural and read well, but the emphasis and meaning are different:

1. First, we focus on the thing (and then do something else with it).
2. We first focus on the thing (and then do something else with it).
3. We focus, first, on the thing (and then on something else).

Answer 2

None of your examples have adverbs in them. That said, English doesn't have a strong word order for the sentence, so long as the subject and object of the sentence are separated by the verb.

In your first answer both are valid and would be parsed to result in the same answer. The former is more vernacular while the latter is slightly more formal, but most readers would understand the meaning.

The second example, 1 and 2 are valid, while the third is not. The comma separation is not required for sentence 3. The first sentence would be best if writing a list, while the second is more used in an argument as a thesis for a paragraph. However, both are valid under either circumstance (the first is a bit simple but at this point in an academic work, it boils down to the preferences of the reader as to which one you should use. Some academics don't want you to make your papers sound sophisticate if it obstructs your ideas from being plainly made.).