So to get a little more in depth on this topic, because local SEO is where I make a big chunk of my money, directory submissions are the easiest way to get a business ranked for local search!
You start with the keywords that have less competition first, but sound good to a business owner.
For instance, (I usually operate under client confidentiality, but this jerk didn't pay me so I don't mind using him as an example) I have a psychic whom I did some SEO for.
If you look type in the keyword "LA palm reading" my client is in the 1st result or "palm reader in LA" he is in the 3rd position. He's even beating out all the Yelp listings. True Love Tarot Cards is the site by the way.
All I did was directory submissions, maps citations, and 4 pages of SEO content a month. In 3 months he was on the first page and not only for that keyword but multiple variations of the keyword. And others like tarot card reader in LA.
I outsourced my directory submissions to someone I trust on the micro gig site and submitted to 160 directories. Did 95 maps citations. And thats it!
Cheers