So you've got a blog and it's been running for a while. You're writing regularly, honing the style and content. Your traffic is slowly climbing, but of course you want more. What do you do next? 

The obvious first step is to submit your blog to blog directories. There are scores, if not hundreds, of good ones out there, with new ones popping up regularly.

You should also submit to free SEO-friendly general directories. Most of them now have a category for blogs, and often sub-categories as well. 

While many of these ask for payment, many don't. And quite a few don't ask for a reciprocal link, either. So you will gain one way links (the best kind) to your blog if it is accepted by these particular directories. 

Certainly, some of these directories will not last, or they may be of low page rank and therefore not that useful. But a certain proportion of them will grow over time and ultimately become highly regarded by Google. So, if you submit to a large number of them this is bound to help your search engine rankings in the long run.

The best part is that you will never run out of new directories on which to list your site. As well as a section for blogs, almost every directory has a section listing still more directories ... You could probably do this for ever and never submit to the same one twice!

You should also join blogging forums. You will learn a lot from participating and if you put your blog URL in your signature you'll rack up many backlinks as well. (Remember that some forum moderators don't like this, so you should check the postings and rules first to see if this is okay.)

A URL in your signature means that you'll be leaving a backlink every time you ask a question, and every time you leave an answer. Google loves forums because they are rich in category specific information, and they have lots of constantly updated and unique content.

Forums do often end up being killed by spammers, however, so make sure that the ones you join aren't dying. And sign up to a few of them at least. It's better to spread those links around, since some forums will rank more highly than others.

I would also suggest commenting widely, and thoughtfully, on other blogs. Most platforms, notably Wordpress, allow you to put a link to your URL along with your comment. Although there is usually a default setting that stops comments being indexed by search engines ("no-follow") you can seek out "do-follow" blogs that have this setting reversed and thereby accrue valuable "link juice" from commenting on them. 

Finding "do-follow" blogs in your niche does take a while, however. I think a better policy is to seek out blogs similar to your own even if they don't have "do-follow" and comment when the impulse to do so is genuine. You will get some clicks coming back from your comments, and since blog owners do read the comments you may score a link from that blogger if he or she likes your site.

There are many, many other methods of promotion. But the ones I have listed are quick and generally effective ways of getting quality links back to your site. This is a crucial first step, since as anyone who's had a blog for a while can tell you the more backlinks you have (particularly from relevant, high quality sites) the better your search engine rankings will be.