The best advice I can give anyone who has started – or is thinking about starting – a personal blog is to write about what you love. When you write about what you are passionate about, it will show through in your writing. The entire process of writing will be more enjoyable as well when you are writing about the things you are passionate about; it will not feel like a chore and you will rarely run out of topics.
If you have no passion for what you are writing about, why are you writing at all? Your entries will come across as boring or flat and you will not gain the readership your writing skills deserve. When you write about what you love, it is a lot easier to sound like an expert in your field.
If you are not sure what you are passionate about, take the time to figure it out. You owe it to yourself, and your potential readers, to know and write about what makes you get out of bed in the morning. If your goal is to make money with a blog, write about what you love and the money will follow… You will have more readers and will write better posts. Great content brings traffic/conversions and when you write about something you love it is difficult to write poorly.