Writing well needs you to...
1. Know a subject well
2. Have an opinion on the subject
3. Have strong feelings that may be 'for' or 'against' an issue, a person, an object, an action, a destination...
You really need to have one or more of the above... and if you do, you're probably still one step away from 'blogging'.
The final step is...
-- You need to understand the medium of blogging well. You need to know computing. You need to find your way around on the internet. You need to have your own blog somewhere on the internet.
If you have this too, well, you're a blogger!
All you need to do is to try and write as frequently as possible and then share it with whoever is in touch with you. If you express well, you'll get readers. If you don't write well, you'll know soon enough and will need to write better.
I think I'll add more relevant pointers to this intro and convert it into a blog post now. :)