It will depend on whether you mean directories like Yahoo or directories like the hundreds listed around the web that nobody ever heard of and nobody ever uses? Seriously, when was the last time someone looking for a new bicycle started their search at link-a-pa-looza.biz? How about never?
The best practices for directory link building depend on several factors all driven by the site you are seeking links for. If you are seeking links for a brand new site at a brand new domain launching for the very first time, then you have nothing to lose and a few decent links to gain by submitting to the many non-descript directories available. Just don’t expect much. Now, if the site you are seeking links for is CNN.com, then there is zero value in submitting to directories. So, what I tell clients is to think of their web site as existing on a continuum. On the far right are sites that are well known already, that have many good links, that rank well. On the far left are new sites with no links at all. Where does your site reside on such a continuum? The more your site falls to the left side, the more those directory links might be worth chasing. The more your site is falls to the right side, meaning it’s already established and pretty well linked, the less likely it is that directory links -even Yahoo- will help you, and the best practice would be to ignore general directories altogether. I have a site that ranks 1st, 2nd, or 3rd for my most important search terms, and I am not listed in any directories other than Yahoo and DMOZ. You will never convince me that all that stands in the way of bumping my 14 year old well linked site up to position one is a few new links from marginal non-subject-specific directories.