How to select your keywords for your search engine marketing campaign?

Try using the Google keyword Tool to start off your project. Personally, I would look at the "Keyword popularity" option. You can get the info of how popular a particular keyword is and its search volume.You can select the specific language and the country for your search. You can see the search volume and how competitive a keyword is.

Yahoo keyword tool will be a very useful tool also:
http://inventory.overture.com/d/searchinventory/suggestion/

Use this tool to select the perfect keywords for your website:http://www.wordtracker.com/ or http://www.goodkeywords.com/

When you are selecting your keywords, remember:
- Don’t use Jargon, use the keywords the end users use to find your site
- Open to new keyword opportunities
- Monitor your keyword performance and get rid of the under performed keyword choices
- Use plurals instead of singular keywords (if you need to pick one)
- Sometimes, working / bidding on highly competitive keywords will not give you good results (Too many people fighting for it!). Instead, use highly relevant keywords with less search volume. It will still get you qualified lead and you will have a higher possibility of ranking higher in search engine.

For me, I will also go to my competitor's web site and see what keywords they are using. Most of the time, you can go to their website and select to view source from the view menu. Look at what keywords they used in their meta-keywords, meta description and Title. You can also type in those keywords in Google and see if they have bought any keywords in Google AdWord. Do the same for Yahoo and MSN.