How To Write A Letter To A Potential Client . Narrow your target demographic as much as possible, considering characteristics like age, gender and income. Mention why the services would be valuable for the potential client. Sample Marketing Letter To Potential Clients For Your Needs Letter from simpleartifact.com If you are a marketing firm, you can target such an institution by offering them valuable marketing services. The beginning of the welcome letter should include the date and the recipient’s mailing address, all aligned to the left border. We write business emails for a million different reasons.