I found an interesting study from an Internet marketing company in San Diego, called Engine Ready, about the conversion rate -that is, the number of shoppers that turn from browsers to buyers. 

It states that conversion rate from paid (or sponsored) links on search engines is 2.03% versus 1.26% from organic (or unpaid) links.

What's more, those who clicked through a paid links spent on average $11 more than the second group. Why? Because when you are ready to buy, naturally you tend to click more on ads. 

This conclusion brings to the table the importance of the Search engine marketing (SEM), popularly referred as pay-per-click, or paid placement on search engine results. (Meanwhile, SEO stands for search engine optimization, a process that seeks to boost a site's traffic by helping it rise within unpaid search results.)

And since SEM can be expensive (especially if choose broader keywords and phrases) here you are some tips to launch your DIY SEM campaign:

• Pick focused and relevant keywords after seeing what customers search.
   
• Use keyword tools like Google's Suggestion and Google Trends tools to get data on popular and seasonal keywords. SEMRush provides a list that other advertisers might be bidding on. EBay Pulse can help to identify keywords and phrases that shoppers use. 
   
• Run tests and monitor your results. Check out various analytics programs such as Google Analytics and Yahoo Web Analytics.
   
• Write compelling pay-per-click ads that gets to the point quickly and encourage people to click over. Consider including inducements such as discount offers, promotions and free shipping deals.
   
• it is best to pick highly relevant keywords targeting only certain prospective customers. Filter out undesirable clicks trying to be more exclusive than inclusive.
   
• Landing page must match up with keywords on the ads. Avoid directing people to general merchandise page; that is source of frustration for shoppers.
   
• Watch out Google's quality score. This is a measurement that Google and other search engines use to determine the order of paid links, and is based on how relevant your keywords are to search queries, the number of times someone clicks on your company's links and the quality of your landing page. It is kind of Google's credit rating. Therefore, you need to align your keywords to your company's products.