1. There's a piece of advice I want to give, and I'm going to give that advice to some degree regardless of the question or situation. Maybe I'll wait for a question where my advice fits, or maybe I won't, but it's a play _I_ want to suggest, so I'm going to suggest it. For example, "use Django" is advice I might give to anyone who asks anything about web apps because I know Django and it's easy advice to give.
2. I really listen to what someone's asking, and give them specific advice for their situation, without letting it be colored by my own experience or the moves that have worked for _me_ in the past.
The second is a lot less common! It's really hard to pay that level of attention, and force yourself to question your own assumptions. But it's also a lot more useful, since it's specific and tailored.
Critically, in a blogging context, only the first mode is really possible. There isn't someone asking for the advice, it's just me writing a blog post for some imagined asker. This is why most unsolicited advice isn't that useful, which absolutely includes whatever blog post you're reading. Including one of mine.