Avoid directories that use the no follow tag as this shows a lack of trust towards your website and therefore will not help you in any fashion to climb the search engines.
1. Relevant Category Listing: This is by far the most important factor when submitting your site. If you have a site related to the jewelry market then it will be better if you list it in the jewelry category instead of the shopping category. Although listing in the shopping category will still help, your link will not be as powerful as it would be if you listed in the jewelry category. Search engines like relevant links from relevant pages (supposedly) and this includes directories. So when submitting your site try to list in a category that is almost 100% relevant to your website.
2. Use Good Anchor Text: Some directories only allow you to use your orignal site name for the anchor text and that is fine by me. But there are alot of directories that also allow you to use keywords in your anchor text. IMHO the best anchor text to use is one that contains both your site name and the keyword you are targeting. For example, if you own a computer repair website then your anchor text should read something like this "Computer Repair from Website.com". Adding your domain name at the end of the anchor text will not hurt anything because the search engines read from left to right so the keyword you are targeting will be read first. More importantly, when you use a combination of both it looks alot cleaner then just using keywords.
3. Use Different Descriptions: Using the same description for every submission will not help much. The main reason you want to use a different description for each submission is because about 80% of the directories out there allow for each submission to include a detail page. Most of the time your detail page will only contain the description that you used to submit your website. If you are using the same description for every submission then you are losing out on the benifits that come from detail pages. So although you might have a 100 directory listings you are missing out on the other 100 you could have from the detail pages alone. In other words you will end up with only 1 link out of a 100 with the other 99 going to dup content. So don't cheat yourself, write a unique description for every submission, the longer the description the more it will help.
4. Take Advantage of Deep Link Options: Many directories no longer offer the deep link option and I still do not understand why that is. But again, there are many directories that still do offer this option so you want to take advantage of it. Deep link directories allow you to link to other pages in your website. This can be helpful if you are trying to rank some of your other pages for certain keywords since the deep link directories allow you use anchor text for your deep links. Moreover, if you use the right anchor text on your submission then you can end up with a pretty relevant detail page, thus making it easier to rank for certain keywords.
5. Don't Sweat The Traffic: Keep in mind that you are submitting to directories to help you rank better in the search engines not get tons of traffic from them. I know alot of us would like to think that we can get alot of traffic from being listed in directories. Now granted, there are in fact some directories that will send you some traffic but who's word can you take for that? The only way to know for sure is to submit your site in order to find out.`If traffic is really that important then I would recommend that you go with the featured listing as these will give you a better chance of gaining some traffic.
6. Don't Sweat The Green Bar: As most of you know google has been making alot of changes in the page rank algo and therefore you will likely see some low numbers on most directories right now. But don't let that stop you from submitting, most of these directories are sure to gain a respectable page rank once google gets everthing in order.
7. Pricing: Because of the changes in the recent pr updates alot of directories have dropped the submission fee to a much lower price. I would take advantage of that, remember, you need as many links as possible in order to rank higher, so if there are directories out there with low prices then go for it, it will not hurt anything only help you out in the long run.
Conclusion: Don't get caught up in all the hype about whether or not if directories are still worth submitting to, I can assure you that as long as the search engines keep using links as a way to rank websites then all links will continue to help you rank higher. Another thing, do'nt get wrapped up in the pr of the directory that you are submitting to, otherwise you will find your site staying at the bottom of the rankings. Again, directories are there to help you with link popularity, if your only focus is pr and not the search engines then I recommend you look elsewhere to get your links from. If you submit to directories in the right fashion then you will see the benifits that come from them. If you are not sure about which directories you should submit to then I recommend that you take a look at http://www.avivadirectory.com/strongest-directories/ which has a list of the most powerful directories on the internet and has been a valuable source for myself and many other site owners and webmasters.
Once again, thanks for reading and sorry it took so long for me post something, things are little crazy around here as I have a new baby girl on the way so I have been spending alot time getting ready for that. Feel free to stop by from time to time and check out what else I might be talking about. God Bless and May the serps be with you.