It all depends on what you want to achieve with your blog: branding? promote your own business? promote other business’s products as an affiliate? just let the world know about you and what you do?
After you have cleared your objectives, you can decide the topic you want to blog about. First of all, it must be something you are passioned about. Let me repeat this: use a topic you have passion for, because otherwise you will lose interest after a few posts and all you have done is lose your time and your money (time is money, right?)
Then comes the text your write, the words you use. You need to use small sentences within small paragraphs so that you can keep your audience interested on your posts.
People also like seeing images on the text they read, so do not forget to be generous about using images. This comes to the next point:
Try to use small size photos, because if your photos are heavy, they will make your blog very slow and this will make people just leave it even without opening. This will also lead to de-index or not index your blog on search engines at all.
Another important consideration is using a great blogging platform. WordPress is by far the best one nowadays. If you do not have an idea how to setup WordPress, you can see this post.