SEO services providers believe that the keywords to be targeted should be decided even before designing the website because it has lot to do with website design and make. The website layout is the first thing that determines the place where you will get the chance to put in the content and the keywords. Also the website designing should be done from the search engines point of view. They like static and light websites as compared to flash equipped heavy websites.
The three main rules for success in SEO are all based upon keywords. The first rule is select keywords related to your industry. This rule is self explanatory still many make the error of selecting wrong keywords. If you are selling mobile phones and wish to optimize the site for T-shirts then how can you expect the visitors to find you?
Rule number two is study properly which keywords receive traffic and try to emphasize them as much as possible. This is important because many times you will find words that relate to your business but not all people will be using the same word for finding you. For example you might feel luxurious gadgets relate to you but for your potential customers useful gadgets might be a more relevant keyword.
Last but the most important rule is to make sure the keyword you wish to optimize has commercial value. In the sense that keyword should be able to bring you some financial gains. For example if you are selling iPod covers then make sure you optimize that keyword. So that when the customers click through they are diverted to the product page. In case if they are not diverted to the product page but some other page then they would not buy anything from you and just do window shopping.
The question popping up is how do you master these rules? There are many keyword analysis tools available in the market. You can use any of them for your study. Make sure you read everything about the tool and its usability before you actually start the research. This will give you preciseness in your work.