Search engines can pick your web site by simple google submit but in that case you will not get keyword rankings and link popularity.
You need to build quality incoming one way links and as per me there is no need to consider pr but the site from where you are getting links should theme based with contnets.
You should also submit in web directories because they are good way to get incoming links as google like links from all sources like sites, directories, links from blog posts, social bookmarking, article submission, press release submission.
Once your web site will be visible in all these sources, your web site will be considered having naturally promoted and you will get good rankings.