Does anyone here have experience with lead generation?

I always wondered how lead generation companies generate the leads that they have and sell to insurance agents, salespeople, and anyone who would purchase those leads.



What are their tactics of operation? Do they have access to online lists that the general layman would not have access to? I will give a personal example.



Part of my job as a loan officer is to locate small businesses that are in need of loans. I work for a lending company that specializes in assisting small businesses to get approved, even in "hard cases" (bad credit, no collateral, no guarantors etc)



One thing that would help me a lot (and I know that this is a long shot) is to somehow access public lists of applicants that got rejected, or legally receive access to private lists, if that is possible. Is there a way to do that?



So I guess my question is a two-part question:



1. In general, how do lead generators generate leads? What are their methods and tactics?

2. Are there any online/offline resources that I can turn to which would actually increase the likelihood of finding businesses in need of my services?



I appreciate any helpful info and tips that I will receive here. Thank you all ahead of time :)