There are no "key" words to use on an image or text. You need to find a way to show that the business is legit and trust worthy.
Couple of items to consider that helps.
- Interact with your clients directly face to face if possible, and/or social media. You need to show there is a real person working behind a web page.
- Let your visitors know how the transaction online is safe through your site (i.e. SSL Certificate, letting them know that you use PayPal one of the leaders of payment processing, etc....)
- Make sure you web site represents the product/service. You don't want to be advertising a professional services but your website lacks professionalism from design to text.
- Let them know your business values
- Let them know about your business through a good but short About Us page.
- Contact details to ensure the clients that if they need help or have any inquiries they can contact someone.
