Style is something personal, which is built book by book, author by author. It also reflects your literacy, in many ways.
I encourage people to use punctuation, like dashes and semi-colons, as well as writing lengthy and complex sentences, but that may not be your style. No problem, as long as you don't simply avoid writing with any complexity at all. You must write something worth reading, and that involves putting effort into your style, to make something enjoyable to read.
There are many things I can recommended to help develop style:
Use semi-colons, dashes, alternatively "—", ellipses ("..."), but use them with care — without overloading your text with them. I myself find it difficult to not include at least one semi-colon per paragraph.
Use hyphens. Hyphens are useful; when there is not a word that describes what you want to say, hyphens can be used to combine words to be used as a noun or adjective. These are far-more-useful-than-you-think words, and can help spice up your writing by drawing attention to a particular detail, similarly to how dashes place emphasis on a phrase.
Do not be afraid to make long sentences. As long as you take time to edit and proof-read to make sure that it is grammatically sound, you are good to go.
Use repetition very carefully. It is a great way to emphasise, but it is annoying to see often or in excess.
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An Unforgiving Guide to Writing
Non-FictionA compilation of tips and rules for writing. Disclaimer: I myself am not an expert writer. I have only been writing for a little over two years.