Don't use CTAs to drive people to your homepage, for instance. Even if your CTA is about your brand or product (and perhaps not an offer like a download), you should still be sending them to a targeted landing page that's relevant to what they are looking for and includes an opt-in form. If you have the opportunity to use a CTA, send them to a page that will convert them into a lead.
Sales leads are generated on the basis of demographic criteria such as FICO score (United States), income, age, household income, psychographic, etc. These leads are resold to multiple advertisers. Sales leads are typically followed up through phone calls by the sales force. Sales leads are commonly found in the mortgage, insurance and finance industries.