In my last job in sales, I tried to acquire a big customer. They didn't respond to my e-mails or calls, but I continued to send them more offers relevant to their business. I used to send the manager a greeting card when they had a bad day, with a small present. I was persistent in my efforts, trying to build a relationship with them. And when they finally needed a big upgrade to their ERP system, guess who they contacted first? They contacted me, and we eventually closed that deal.