We are building a web app where lead gen will be a major component. I would like to get more information about implementing it
Depending on how readily available the leads are -- one way is to outsource the work on a site such as elance.
Another method would be to create an affiliate program and pay a commission for leads.
For a quick and simple (and cheap) solution, you can download a template and gather emails of perspective customers. You would obviously need to give them a compelling reason to fork over their email address.
It depends on the type of leads you're planning to generate.
If someone is looking for advice on best web hosting, then you probably can get away with a few affiliate links and get paid when some one follows one of those links and signs up for service.
I run a site that deals with highly specialized market research. Often we outsource qualified leads to firms capable of fulfilling the project. Often email request is the first step, followed up with Account Executive's call back, who takes it from there.