For gen peds, the way to increase business is to see new babies. Reach out to the OB groups in the area and let them know that you're seeing new patients and consider getting credentialed to round in the hospitals. If you have a niche interest in something (particularly psych meds, ADHD, LGBTQ health, teens, obesity, etc) then advertise that bc a lot of people who don't want to manage those populations will send them to you. If you're passionate about LGBTQ health, then advertising at local LGBT centers will net you some referrals as well.
I'm subspecialty and walked into a group practice with lots of referrals, but I've been working for 4 months and today in my full day clinic I only saw 3 patients. So it does take time too.