The world of eCommerce is a vast one that includes a diverse range of businesses. This can make giving broad advice about that world a tall 
order; perhaps it’s one that should even be avoided. However, one topic that everyone in eCommerce should know about is Google AdWords.
If you’re unfamiliar with how Google AdWords works, it’s a simple enough concept (though it can get complicated quick). Google actually auctions off the right to show up on their results page for popular keywords. Depending on how much you bid and the quality of your site, Google will decide if your ad will run and where they’ll put it. How much you actually end up paying depends on the amount you bid, the quality of your competition and how often people click on the ad.
Now, here’s where it gets interesting. Many people use Google AdWords for no other reason than to find out which keywords are hot for their market. If you have an established eCommerce site, you may already be using analytics to find out what words bring customers in. These might be good keywords to bid on with Google AdWords.
However, if you’re just starting out or want to see what other keywords could help, you could log into Google AdWords and start searching for which keywords your competition is paying for. Remember, just because competitors may pay to show up on Google’s results page doesn’t mean you can’t still achieve a traditional rank. Plenty of companies have the number one spot without ever paying for AdWords.
Google also supplies its users with a ton of information when it comes to keywords. Many people only focus on one, though: click through rate (CTR). However, understand that a high CTR doesn’t say anything about conversions. In fact, some keywords may speak to a part of the demographic that is only curious about your product or already owns what you’re selling. So take all the metrics Google provides into consideration.
Remember, too, that winning good words is only half the battle. You also need to optimize the ad you’ll be using. Include a call to action and be sure the link involved brings customers to your landing page (which must also be spectacular). Otherwise, you just went through all the trouble of securing a keyword for nothing.
Whole books have been written about Google AdWords and only scratched the surface. However, the above should be more than enough to set you off in the right direction or reconsider your current AdWords strategy.
Sources:
http://www.wordstream.com/articles/what-is-google-adwords
http://blog.whitesharkmedia.com/28-tips-for-adwords-beginners-i-wish-someone-had-told-me-infographic