You can make a whole page for your testimonies, or can put them throughout your site. If you are able to offer a free trial period with your service or product, then you have a very big advantage against your competition. Let them use your service or product for a trial period and if they are happy, charge their card. This will increase your sales, but can also increase the amount of scamsters you see trying to use you. You might also want to make a contract to fit your needs if required.
People are afraid to give out their credit card.
If you have a contact page or on your index page that has your company contact information, it gives the customer something to believe in. It shows that you really exist, and gives them the opportunity to look you up in the Better Business Bureau. If they do it, it will really make them feel safe, because the BBB is a very well trusted business organization that shows off good solid companies. It also gives the customer a chance to find out how to contact you if they ever need help, if they decided to purchase your service or product. If you sell a product or service that has a good reputation, then try to use the name as a selling point.