I've found that most of our clients seem to come to me via word-of-mouth and we actually dont focus very much on advertising at all. Handing over a business card to a stranger in a shopping mall or putting your link in a Forum signature seems to do the trick for me. Other places I've found to be very helpful are those boards in big shopping centres which are prodominantly used for Job applications, however a big A4 full colour page usually is eye catching enough to draw a decent amount of attention. If you are that way inclined, you could also try and put a banner across the side of your car to try and hook a few customers. I know someone on this Forum commented about that a few weeks back and said that he found it to be very effective. Other than that, keeping in close contact with big companies and 'offerring' out your services, seem to be fairly viable options. I work mostly in the design side of my business and find that whilst I am browsing the web, if I find a really bad-looking website or one that has fallen into dis-repair due to the difficulties encountered trying to update a website without a CMS, I will email them and offer them a site with a CMS making it as easy as changing a text field to change your data. A happy client will most probably (and hopefully) put your name on to friends of his or his colleagues until eventually you get your name out and start to get customers without needing to put a big push on advertising sales and instead focus on the quality of your service.
In the web development industry, I have found that putting out software which is 'OpenSource', but keeping your company's logo on the product or page also tends to loop in a few customers here and there. Prodominantly, however, I do rely on Word-of-Mouth recommendations as they seems to be the most effective method of hooking customers.
I also try to keep in touch with my customers by constantly offering them updates or graphic work for their site, therefore ensuring that they dont forget out our business (and I will add, this also keeps the cash flow going).
Most of all, I find that offering clients discounts on designs and hosting, in exchange for a banner or frame at the bottom of their site, usually keeps a company's name in the fore when it comes to marketting, as well as showing that (in the case of design) your products are of a decent quality!
I'm happy if people want to tear this post to threads (no pun intended) but these are the things that I have found (in my experience) work!
~Equinox