In the end "leads" are just people that are interested in the products you sell, simple really.
There are ways to get leads for free, I recommend you always tell the person where you got their email address from - example - you join a list building site, tell them you are contacting you as they showed an interest in blah blah product via blah blah website - if they say they have no knowledge, apologise & make sure you put them on a "send no email to" list!
One sure fire way to get leads is offering an ebook that has something of value to your niche:
You can get FREE EBOOKS HERE!: