Yes it is realy important if you want to rely only for SE traffic.
There are some techniques in keyword suggesting and here I have tool that will help you to generate metatags and golden keywords:
http://www.webmaster-money.org/tools..._generator.php

Also this articles might help you:
http://www.webmaster-money.org/artic...te_Part_1.html
http://www.webmaster-money.org/artic...te_Part_2.html

I hope it will be helpfull