Writing articles for sites that allow you to have a signature link at the end is a good way to gain incoming links, however it isn't for all sites and like most other link building methodologies there is a darker side to it.
With almost all Internet marketing techniques there is the easy way, and the hard way, and the hard way is almost always better. In this case many article directories or article submission services have popped up to cater to the lazy out there who do not want to spend the time looking for actual real places to submit articles. These article republication sites offer almost no value in linkage, no traffic, no link weight, nothing.
When you submit to these sites your article will be republished in countless other worthless places and in the end any signature link you have will end up looking more like spam than anything else.
Yet, content site owners need content, and article writers want good incoming links, so there must be a way to bring them together, right? Yes, but it involves work on both sides.
Good content sites get that way by not publishing every horrible 500-word fluff article that barely scratches the surface of useful information that comes their way. Good content sites get that way by not publishing content that is published in a dozen other places. Good content sites get that way by exercising editorial control over what they publish and by seeking out unique content.
So, there are links out there to be had on good content sites, but you need to be willing to put in work for them. That means writing a useful unique article for publication. You may even be able to negotiate payment though most webmasters understand the value of a signature link from a good content site and will take the value of the link into consideration with any negotiation for payment.
Another thing you do not want to do is write an article that reads like a press release for your business, if you want to write a press release see the previous section. Webmasters who exercise real editorial control are savvy to such tactics and will likely reject your submission.
So, you see, with article writing you get what you pay for, or rather what you put the work in for. If you spend no time or effort in writing an article you can get it published on generic article directory sites or poorly ranked content sites that no one uses or considers an authority, the links from these sources will be next to worthless. Or, if you put the work into writing a good article you can get it published on a good authority content site that probably has a good deal more link weight & traffic to pass your way.
The best thing you could try to do, especially if your site is complimentary rather than a direct competitor to a content site (such as an ecommerce site) is work out a regular contribution deal where you provide one good article every month or two to a content site webmaster. A reliable regular contributor is valuable enough that the webmaster may allow you a little more freedom in promoting your business.