How to increase web site traffic in yahoo or google search engine

Hi to everybody, im currently having my industrial traning in a company. Last few days, my boss asked me to do something about my company web site. Due to poor ranking in yahoo and search engine, my boss called me to do something in order to increase the traffic of web site. I found some solutions such as adding meta tag, modify the keywords, or maybe it's about the main page content problem which caused the search engine can't find our web site even many sugggested key words have been used. So please if anybody know it,kindly help me to find out which is the exact answer in order to increase web site traffic! Thank you very much!

See below

http://www.google.com/intl/en/webmasters/

HTH