During the last 10 years of the web, a lot has changed. Before, webmasters were able to rank high on Yahoo simply by submitting their junk website to hundreds (or thousands of) web directories. They were also able to rank at the top simply by spamming (to some degree) their way through. Now times have changed and because the search engines are more intelligent, these techniques do not work.
These days search engines reward you for providing unique content and punish you severely in case you have spammy content. In short, any technique which is undertaken only to helpÂ you with the rankings is frowned upon and is less effective these days. Let us look at some examples.
The first technique which has stopped giving SEO benefit to some extent is directory submissions. Directory submissions have been used and abused by everyone. Most of the content in most of the article directories is spam in the sense that it is put up simply to get a link to a website. To make the problem worse, a large percentage of directories are not actively managed by their owners. Google knows this and tries not to give too much weight to the directories any more. If, however, you submit your content to high quality directories like GoArticles and EzineArticle, you will get a considerable amount of link juice.
Another technique which is said to have reduced effectiveness is using reciprocal linking. Although reciprocal linking used to have a lot of value, it openly tells the search engines that the links are not natural. And because search engines like natural link building more than ever now, this technique wont really help.
Even keyword stuffing in your keyword tags also does not hold any value. It is the same old story here as well: People put in so many keywords in the tags in their SEO attempt that it just neutralized its effectiveness. I do not think that Google penalized you for keyword stuffing in your tags, but I do know that the benefits of doing that are little (if any).
Lastly, crappy links do not help you anymore. Unlike old times, it does not help if you have thousands of PR 0 incoming links to your website. Techniques like link farms which might have benefited you before will severely get you penalized now. You have to start competing on quality and not quantity if you want to rank high.