I feel like the people who are best at this have a constant rhythm around staying in front of their customers. Whether it's commenting on their LinkedIn, sharing resources, checking in, they have a committed effort to do it, so when they need to reach out in regards to a "sales" reason, they already have the "in". Would love to hear what others have to say!
I would recommend finding ways to connect with your customers. Having something in common, or maximizing the relationship outside of the work environment will help you to succeed better within the competitive market.