I mean, I do read some articles about how to distinguish between those three, but I found that when I wrote stories or blog entries, the rules that I've read is impractical to remember. I found myself going over all the articles over again to decide which one to use, almost for every single sentence.
Can you give a very simple principal rule of thumb, which may cover a large portion of their usage rules? I understand that there's no single "one rule over them all", but at least "one rule over most of them", which I can remember while I write sentences, is already fine by me. :)