Lets take an example to understand more on this.
Imagine you are writing about Windows 10. The best practice would be to pick what about Windows 10 you are writing?. There are lots of things you can write about but to make people search for it, first think what people might search for?
Here are few keywords people may search for the Windows 10.
Win 10,
Windows 10,
10,
Windows,
Microsoft New Operating System, etc.
Now those were the keywords, people might search for. and if you were to search for, those were the kinda things, or the keyword, what you might search for.
Also this is not enough. Things what you might want to write may have already been written by someone, since there are lots of writers now. The next question that should strike your mind is, what makes it unique from other website? If you are able to find out this answer, that's the key to the Blogging. You will be able to express things in your words and people might be actually interested in your content.
Now, we need to pick up the right title, for the post that you have typed. Now this is very important as the Blogger will take the URL from the website title(Post Title). If you choose to simply add few things, then you will fail to get people search for your website.
So the ideal way here, is to pick the topics which people will actually search for it.