You get to 80% there (numbers pulled out of the air) by just telling it to do things. You do need more to get from 80% there to 90%+ there.

How much more depends on what you're trying to do and in what language (e.g. "favourite" pet peeve: Claude occasionally likes to use instance_variable_get() in Ruby instead of adding accessors; it's a massive code smell), but there are some generic things, such as giving it instructions on keeping notes and giving them subagents to farm out repetitive tasks to prevent the individual task completion from filling up the context for tasks that are truly independent (in which case, for Claude Code at least, you can also tell it to do multiple in parallel)

But, indeed, just starting Claude Code (or Codex; I prefer Claude but it's a "personality thing" - try tools until you click with one) and telling it to do something is the most important step up from a chat window.