Before considering a well thought out plan, develop a set of personas for your clients. Through the development of these models, many questions and answers will become apparent. I would advise against asking yourself: How would you like to be touched by your vendor(s) because you are not your customers.
Remember that there is no one way of keeping in touch as various personas (models of your customers) will want to be “touched” in various ways. Some will like the idea of an email whereas others would appreciate a phone call and yet others will expect a face to face meeting, some may appreciate news or information relating to their business.
At the most basic level, developing personas allows you to create content and messaging that appeals to your target audience. It also enables you to target or personalize your marketing for different segments of your audience. For example, instead of sending the same lead nurturing emails to everyone in your database, you can segment by buyer persona and tailor your messaging according to what you know about those different personas.
Here's a great article to get you started: https://blog.hubspot.com/marketing/buyer-persona-questions