A client asked me "What is a good quality link and how do I get a good quality link. You said reciprocal links were no good is that correct?". This was my response.
Reciprocal links are not always bad. If a site selling diving holidays links to a site selling wetsuits and the wetsuit site links back that's normal linking. Where reciprocal links look spammy is where a site about bird watching links to a site selling birthday cakes. Relevance is the byword with reciprocal links.
Now the thorny question of 'what is a good quality link?'
Your dream link would be an article on this page about how quality curtain poles add so much to the feel of a room, where the words 'curtain poles' link to your homepage. That's a pagerank 5 page, that means it's trusted, and the value of that page linking to your page could be significant.
Your complete waste of time link would be being one of the footer links on this page, pure spam. Of course the BBC are not likely to offer you a link from that page whereas that spam page would no doubt sell you a link for thirty bob.
In the end it's the quality of your content that dictates the quality of the links you attract. Eric Ward sums it up perfectly in this link building article.
In a nutshell to attract a great link you need something worth linking to on your site. Something that adds value to the page where the link is coming from. This takes us full circle back to quality content because there's no point wasting time asking people with quality sites to link to your site unless your site is offering something unique. This is why people resort to buying links, it's quicker and takes less work so long as you have the budget.