Just like Elcidofaguy has already mentioned above, email marketing is one of the best ways to promote clickbank products. I like to break it into 3 simple steps for people who don't understand the whole email marketing process/funnel.
Step 1 is simply your bribe and squeeze page. Your bribe could be anything that is closely related to the product you would like to promote, it could be a free book, video, audio etc. it also has to be valuable content, that will boost your trust. Then a squeeze page is simply the one page website you'll use to capture the visitor's name & email address.
Step 2 is building a really strong relationship with your subscribers, now that you know they're interested your job is to convince them to buy. The easiest way is to give them an ebook/pdf then send them a video series explaining the things that are in the free book you gave them visually (with videos or even audio). Via an autoresponder.
You simply send them valuable content on a daily bases but some days you don't send them content instead you promote a product. But take it easy and promote 1 product for about 15 days (promotion emails mixed with valuable content in 15 days). So you'll be promoting 1 or 2 products per month and make sure the content you send is related to the product you're promoting and offer expiring bonuses to increase conversions.
Once you have your funnel setup then you can move to step 3...
Step 3 is all about traffic. My advise, choose different traffic strategies, use them all till you find one that works really well for you. Once you've found one then stick to it and master it then generate a good revenue. Now from there you can explore other traffic strategies knowing that you're a master in Facebook Ads for instance, instead of being jack of all trades and...
One thing you have to know about traffic is that it's all about testing, good for you if you find something that works well first time you try it. But be prepared to fail and don't be afraid of failure, it's the best teacher.
Once you master these basic steps then you can move to more advance stuff like split testing and tracking. This is the same thing Sid said but in a more simple way to understand. Hope that helps