Five years ago I came into contact with a market analyst company that specialized in my particular area of expertise. To their credit, they kept after me over the years, which finally paid off:
2001 - Initial engagement. Provided overview of their services and market report summary. The start-up I was at went belly-up in 2002, and I sent that bit of information to the analyst since it pertained to the most recent report they were writing (which tracked companies doing business in this segment). They promised to keep me apprised if they heard of any job openings in the area.
2002 - I landed at a mutinational Korean conglomerate that already had a stable of companies they bought reports from and wasn't interested in another one. My contact at the original company still kept me apprised on the market, and I sent data their way as well on what my company was doing for inclusion in their reports.
2004 - I changed jobs to a U.S. based company, and tried to convince my management to buy a report from this company. However, my company started slashing costs almost as soon as I joined and wouldn't okay funding for market reports. My group - and job - were cut a year later.
2005 - I was consulting at this point and badly needed this company's market data for writing my own report - and making money. But as an independent consultant, I didn't have the thousands of dollars to pay for one of their reports. They gave it to me. For free. No strings attached.
2006 - The company I was consulting for hired me, and I used my influence and position - and the quality of the reports - to convince my company to buy not one, but two reports from this company.
The lesson here is probably more about networking - and keeping up with your contacts - than about the "sales process". My contact gave me data over the years and came through with a big favor when I needed it. And I was sure to return the favor when I was in a position to do so.