I used to work for a telemarketing company when I was 18 selling long distance. About 20% of the people cursed me out as they did not want a telemarketer calling their house. That job was not fun but it helped me get over my fear on the phone. I owe a lot to that job and in life we can attribute a lot of our growth to the times where things were NOT that fun.
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.