There are no two ways about it -- trust building takes time. That's why we have sales cycles - why most people don't buy on the spot. Those web merchants who have learned to write compelling copy and the one-page letter approach to trust building have been on to something, because the letters are designed to build trust. A percentage of people who read them will buy. And with a worldwide audience, all they need, and expect are a percentage.
If you are selling in person and by phone, you need to show the potential customer that you have a solution that will fit their needs, (assuming you do) - and that you have helped others solve their business issues as well.
The rule of thumb in sales research has been that it takes 5-7 "touches" to make that impression for the customer to buy. Touches are the times you contact the buyer in some way -- be it a mailing, a phone call, or in person visits. Some research done by Jim Cecil of Nurture Marketing about ten years ago indicated that once you have around 13 contacts with the prospect - a large number will now work with you. You've stuck it out - built trust, and each contact reinforced your message and value.
Remember the most significant factor for long term customers and then target wisely. Start with 25 prospective companies - or 50 or 100 if you can consistently follow up with this number of contacts. If you are a services provider, target 25 to 50 potential alliance partners and consistently follow up with them - it works the same way, except that these contacts can refer you to many others. We'll talk more on that later.