I've been suggested that the best method for selecting keyword to optimise the site is using count and competition analysis of the keyword for that Search engine. I want to know which is the best method for selecting keyword for PPC program if I want to bid for $0.5/click. e.g(Online Marketing}in google adwords..

If you are only bidding $0.05 per keyword you will need to find keywords that not many others are bidding on. I would suggest using keyowrd suggestion tools like those at prsearch.net and wordtracker.com to find such keywords and then check the google search results to see if how many others are bidding on them. For niche words you want to be on the first or second page to get any traffic.

Yes, I think if you are going to get much traffic from 5 cent bids you will need a lot of niche keywords because they are not searched for that often.

Word tracker recently came out with a great FREE version of its keyword suggestion tool.
Here it is: http://freekeywords.wordtracker.com/

Geofferson Marcy
www.advaliant.com/geoff