Hi
Since we do performance based marketing, one important part of the game is about getting as high CR as possible, keeping the high quality of our referred traffic .
Therefore the Calls-To-Action have a prime role for the success of a campaign.
Remember that the Call-To-Action is the place where you direct people to the action you want them to do,
so you should keep it clear, short and supply them an easy way to do it. Here I gathered a few tips for you to consider when creating your Calls-To-Action:
* Action Verbs are very efficient in Calls-To-Action, such as: click, register, learn, download, visit.
In addition you can further focus your possible customers by adding words like 'here' (download here), make them curious using words like 'more' (learn more)
create a sense of urgency with terms like 'now' (subscribe now) or attract your public and stress out the benefits of your offer using words like 'free' (open free account)
* Place them in strategical/easy to find places. In my opinion, if you use a LP for example, the Call-To-Action should be visible one time without the need to scroll down the page and if your space permits it you can then added it in the down - side of the page.
* Design them to be visible and push to action. Few ways to do it would be by adding arrows to the CTA button or other powerful designs, give them contrasting colors from the rest of the page/creative while making sure they still look like part of it.
Wish you all the most efficient CTA ever 
Cheers,
ilana