Do not fear commas or the word “said.”
Further writing advice:
– vary sentence and paragraph structure.
– avoid re-using uncommon words (they stick out much more than the familiar ones).
– adjectives and adverbs are your frenemies–not always to be avoided, but dangerous, so handle with care.
– just because Austen or Shakespeare or whomever broke a rule doesn’t mean you should break it–at the very least, you should understand what it is and why it exists, and make a conscious decision.
– character! character! character!.
– sometimes “it’s cool” is a perfectly valid basis for authorial decisions, sometimes not–exercise judgment.
– don’t use words you aren’t familiar with; you should know the precise meaning of every word you use.
– when you do vary your dialogue tags, the new tag should still refer to speech: replied, whispered, shouted, etc, not smiled, chuckled, considered.
– realism and verisimilitude are not the same; whether something really happened or not is largely irrelevant to whether it seems realistic, and that’s what matters for the audience.