Is that even a real question?
If you ask 100 writers for advice on writing you’ll get 100 different answers. Writing does have rules; however, it is a very subjective craft, even within genres.
Each writer has a style. Some are similar to other writers. Some try to copy other writers. Some go out of their way to stand out from the crowd and be as unique as they possibly can.
How do you decide where you want to fit into this crazy roller coaster? Pick something. If you’re the type who tests the water before getting in, you may want to start with writing something you know. Something familiar may help you get your feet wet before you dive into the deep end. If you like to push and challenger yourself, then go for the high dive and jump into something unknown.
Write what you know. Write what you don’t know. Write about what you hate. Write about what you love. Write what scares. Write what makes you happy.
Regardless to how you try to start, the important thing is that you start. Get those words on the page. Whether you’re writing science fiction, romances, news articles, text books, greeting cards, whatever it is, just start writing.
Try to eliminate as many distractions as possible. Clear your writing space. Clear your mind. Hide your to-do list. Whatever it takes so you feel free to sit still and generate words, do it.
I think the piece of advice I like best is to write what you want to read. It is impossible to write one thing that will please everyone who reads it. Write to please yourself. Write what excites you. Write with passion.