Almost all marketing comes down to whether people know you. (As they say in Hollywood, it's not who you know, it's who knows you.)
And they need to know you for good things, not bad. That's why all of those "power" efforts to spam announcements of articles don't work so well. If all anybody sees of you is an ad, then they think of you as an ad. They start to think of you as the spam they didn't want with their breakfast.
So as I mentioned in previous backlinks post about signatures, just having your contact information available as you interact normally is a great way to start. You can use the same principle, though, well beyond email.
Commenting on blogs is an easy way to do this. Different sites have different rules, but they almost always have a place in the comment form to ad an URL. It's usually not displayed, but rather it's embedded in your name when you comment. So it works like a sig, in that if somebody wants to know more about you, they just click on your name and they'll be taken to the page you entered there.
There are two very important things to think about before you do this, though:
One: Nobody is going to click on your name if your comment isn't interesting or useful. If it smells even a little bit like spam, the proprietor is likely to delete it, too. Your comment should be relevant, and interesting in and of itself. It should NOT say "hey, here's an article that relates to this topic, go and read it." One way to make things interesting is to give an opinion. It can even be a controversial opinion as long as it is respectful. (Again, the proprietor will delete disrespectful comments.) "That's a great point, although I prefer this for that reason" is a great post, if your reasons are well spelled out.
Or when in doubt ask a question. Even if nobody answers, you have at least contributed to the usefulness of the discussion.
Your other major issue is that you can only put in one URL, though, so which page do you put in? Some people like to put their article that is closest to the subject, and that's a pretty good idea, although you really have to be prepared with a list of possible URLs at hand whenever you go reading blogs and newspapers.
This is why many people end up creating their own web page or blog, where they can put an index of articles. That way they can concentrate on promoting just one URL. Other people promote their eHow profile page.
One consideration: many blogs have restrictions on who can comment. You may have to have a Google Blogger account - and if so, the link always goes to your Blogger profile. It can be good to set up a profile with appropriate links in each location where you might want to comment on blogs - Blogger, LiveJournal, etc. Many blogs use Open ID, which is a site where you set up an ID account, and it does something similar across a wider range of services.
Profile pages are as important as sigs. I'll be the first to admit I don't make good use of them, but the masters of marketing DO, and if you are serious about marketing, you should always be thinking about your profile pages. Remember that the key to marketing is that you want people to like, or at least trust, you. They will be interested in your product only after they find out you are a person who doesn't waste their time.
Next time I'll talk a little about using Yahoo Answers as a promotional tool. (Just remember, as with any community, they HATE SPAM at Yahoo Answers, and you should only use this to genuinely answer questions. If you don't do this right, you could lose your whole Yahoo account!)
Previous backlinks posts:
What is a Backlink?
Backlinks - blogging
Backlinks - signature files