I am going to assume that you are talking about link trading, where you agree to link to someone else’s site in exchange for a link to yours. This is a really loaded question but I will give a brief explanation of some ideas that are good and some that are bad. If you have a site about the Amazon rain forest and you get an offer to exchange links from a site about saving the environment then it will most likely benefit both of you to exchange links from a prospective of traffic and relevance of the two sites. However if you get a offer to exchange links from a site about dog care then there is little reason to exchange links with them in terms of increasing the value of your site for the terms you want to rank for. That doesn’t mean you shouldn’t trade links with them, if they have a nice site with lots of visitors then it won’t hurt unless they are a much lower pr site than yours. If they are a higher pr site than yours then you may want to seriously consider doing the trade.
One of the benefits of being a member here is that you have access to a few directories that you could offer to put their links on in exchange for a link to your site. You could offer to add their link to
www.coolfetch.com www.autosix.com, and
www.reallylinked.com in exchange for a link to your site. It is good for them and good for you. Make sure that you choose the correct category for their link and put CAB Member in the title so that we know it is coming from a member here, otherwise we may deny the link or suspend it. We will take the CAB Member out of the title before the link goes live on the site.