Writing a successful blog will require dedication and hard work.
Pick a Topic you're passionate about.
When starting a blog you should pick a niche or topic that you're passionate about. If you're passionate about the topic you will not get bored so quick on writing content for the blog and for a successful blog you need a lot of quality content to be successful.
Pick a topic you know a lot about.
Another thing you should consider when you're writing a blog is to pick a topic you have a lot of knowledge about.
If you know a lot about the topic or niche you can write quality posts that will help solve peoples problems and that's what you should do. You can still write on topics you don't know a lot about since you can do research and learn more about those topics.
Write your blog in a high paying blog niche.
When you want to make money from blogging you should choose a topic or niche for your blog that has high paying cost per click ads.
Some blog topics pay more per cost per click than others.
If you choose the right niche for Adsense or other ad networks you can get $10.00 or more per click sometimes.