Show a pop-up just a couple of seconds after people enter your webpage, this usually gets the job done. However, to be sure also add a pop-up on the exit, if people move the cursor to exit have the pop-up appear, this with the scarcity hack will help you gain more subscribers. Have a pop-up in the guidelines of your product, if a customer is reading your content they are probably interested and looking to understand it, add a pop-up to help them with execution. Finally, have a ‘Need help?’ pop-up for those customers who are scrolling up and down your page, there is probably something they are looking for.