For me the number one thing I try to focus on is _naming_. If something is hard to name, it's likely hard to understand or overly abstracted (misdirected). If something is easy to name, it likely follows [insert any software development "best practice" here].
What's a good name? I love the phrasing from _Elements of Clojure_ by Zachary Tellman [1]
> Names should be narrow and consistent. A *narrow* name clearly excludes things it cannot represent. A *consistent* name is easily understood by someone familiar with the surrounding code, the problem domain, and the broader [language] ecosystem.