There are many ways in which this can be accomplished; these include:
- Using the Signature box on forums
- Posting to relevant directory sites
- Link Exchange Programs
- Paid Backlink Robot Systems
Using the signature box on free forums can be a highly effective way to gain free traffic for your website, because every time you make a new post, the signature is included at the bottom, and each new post counts as a new backlink.
This means that in order to get say 2000 backlinks to your site, simply make 2000 posts to a forum. Although this seems like a large number, if you make 10 or so a day, it soon adds up!
Posting to relevant directory sites is also a good way to get both backlinks and traffic to your site, however most directories require you to wait a while for approval, meaning that this can take a bit longer than using forums.
Another way to gain backlinks is to use link exchange programs, however my advice is to use these sparingly if possible, because these sites often require reciprocal links, which can result in a messy webpage.
This is inadvisable because it is thought that Google penalises sites that have more than around 100 external links on them.
In fact, there has been recent news that Google is actually targeting link/content farms and making it a lot harder in general for sites to be listed in their index.
Also, it is not just the number of backlinks that counts, but also the quality of them, meaning that backlinks from PR9 sites would be more valuable than say backlinks from PR2 or 3 sites.
Google, in particular, seems to take notice of the ratio of outgoing links to incoming links on specific pages of a website when indexing them. This is mainly done to prevent irrelevant search results from appearing on search engine results pages (SERPS).
For example, if a page contains 20 outgoing links and 2 incoming links, Google would mostly likely consider this to be a junk or spam website and not index it.
A good example of this is a blog or forum that does not have the proper security in place, i.e. posts are not manually approved where necessary, resulting in junk posts and links.
It is worth noting here that WordPress automatically puts a nofollow attribute on posted links. Having a nofollow attribute on a link means that search engines will ignore it when weighing up the links ratio on a page.