Where do you put a comma?

No comma at all is absolutely necessary in that sentence. Some grammar guides advise against using a comma when two clauses that could be sentences by themselves are joined with the conjuction "and." Some prescribe it (including Grammerly and Purdue OWL websites, to pick two). I would allow it either way. However, I would also drop the repeated subject "i" if I left out the comma:

I went to the store and came home with a new hat.

I went to the store, and I came home with a new hat.

The only sentence of the three that seems wrong is number 2 -- but only because at the present time, commas are less likely to be used than they were 50 or 100 years ago. At one time, additional punctuation was common. Now, many commas that would have been used previously, and which are not incorrectly placed, are omitted as unnecessary.

Look at popular writing, such as news and feature articles, to see the less-is-more trend in punctuation.

Or

Look at popular writing such as news and feature articles to see the less-is-more trend in punctuation.