There are certain things that you should take in to account while building link popularity. The directory submission technique on the search engines is one of the widely used and reliable techniques to attain business. These tricks work in the favour of your company giving you the required visibility and traffic. Blogging, forum posting, social bookmarking, article writing and press releases are some of the widest applied tools to generate traffic by the SEO's.
Exactly thats what we call "High PR Dofollow Link Building"......it can take any website on top of search engines if done carefully and with consistency.
Yes very necessary techniques and keep doing link building. also Link Exchange. Keep providing good quality content to your site visitors.
Contextual links work best. Sure you can get a lot of links quickly from directories, but not sure these are of best quality unless they are targeted to your site's niche.