1. Poor marketing
2. Poorly handling buyers
3. No system for converting interest into offers
4. Overpricing

All 4 spell: N.O S.Y.S.T.E.M.

I guarantee that simply offering terms doesn't make a house sell either. If you have the greatest terms in the world but you put the signs in your closet, how many people are going to call? Marketing is what separates 99% of FSBOs and agents, and top producing agents and investors.

Let's address them one by one with a few ideas:

Problem #1: Poor marketing
Solution: Dozens of signs, flyers, direct mail, newspaper ads, website showcase, fax/email blasting every buyer's agent in town.

Problem #2: Poorly handling buyers
Solution: Website with tons of pictures and complete descriptions, 24 hour recorded information hotline, mass viewings hosted in such a way to create competition and excitement.

Problem #3: No system for converting interest into offers
Solution: Either properly screened individual showings (they should be prepared to give you a deposit and sign an offer on the spot), or a competitive bidding system.

Problem #4: Overpricing
Solution: Explain to sellers that the only to get the highest cash price is to create competition between buyers and allow them to bid the price up to the true market value. There's no way to guess at what the market value is (even with comps and appraisels), buyers set value, and competition eliminates bargain shoppers. Thus you get the highest possible price that the market will currently bear. But this is only possible with all of the above already in place.

The fact is that with a little effort you can out sell all but the top producing agents (because they usually have a large existing database of buyers), and with that effort multipled by some time, you can out sell those top producers too because you will have your own database.