Link exchanges are a well-known way of promoting Web sites for free, but they come with a cost other than money.

Two common ways of exchanging links are through link exchange networks and the simple trading of links between two sites via an agreement.

Numerous link exchange networks exist and can be found through search engines. They typically require that you register your site and that you provide a link back to their site.

The basic service often is free. The network makes its money through advertising on its site and especially through upgrades that come with a fee.

Once registered, you can search for another site with which to exchange links. The process might include searching a link directory and submitting a request via the network to the sites that appeal to you.

The other site has the option to accept or reject the exchange. If it accepts the exchange, both sites put up the link and have it verified by the network before the agreement is finalized.

In a similar way, other sites can contact you with requests to exchanges links. Again, you have the right to accept or reject the link.

The key to agreeing to an exchange is finding a site that has related content, quality content and a decent ranking with the search engines. A link from a quality site often can help boost the search rankings of your own site. Likewise, links with low quality sites can result in reducing the search engine rankings of your site.

While linking with a quality site has obvious benefits, there are downsides to a link exchange network. You are likely to receive numerous requests for exchanges from low quality sites for every one that is good. You have to ensure that the site that links to you will maintain the link, and you have to make sure that you maintain your own links back again -- i.e., don't lose them if you rebuild your site.

An attractive alternative doesn't involve an exchange network. A direct agreement with another site has the benefit of establishing a high-quality link. Contacting these sites directly can result in a small number of links that are easily maintained and drive a high volume of quality traffic.

These relationships can be expanded into full partnerships that can include content sharing, banner exchanges and sometimes even advertising agreements. Although partnerships take more work and require more detailed agreements, they also potentially bring significant benefits.

A link exchange network typically requires a small effort for numerous links that bring modest results. The right link exchange partnership can make a major difference in total site performance.