The way to remember that is that the link is important.

For example, [[www.example.com]] makes sense.. it will render as www.example.com that hyperlinks to that link. But [[link description]] is useless by itself.

So.. put the more important thing first, the link:

    [[www.example.com]]

Now, if you also have a description text for that link, put that afterwards..

    [[www.example.com][link description]]

Hope that helps.