Monkey Business Images / Shutterstock.com SAN FRANCISCO — Client relationships — everyone talks about them, but they don’t necessarily maintain them to the best of their abilities. Sending clients texts on their birthdays or befriending them on Facebook shows that you’re at least attempting some sort of relationship, but being extra nice and attentive isn’t something most people plan out. Having a spreadsheet of clients’ interests, birthdays, family members and the last date you’ve spoken with them might sound like a lot of work, but according to Jena Casey of Intero Real Estate in Houston, that’s exactly what to do if you want to increase referrals. “I’m not building my business off my first $15,000 check,” she said at Inman Connect San Francisco. “I have a family business t…