Can someone please help me with being a new stepmom?

My step son is almost four. We see him a couple of times for a few hours every week and every other weekend he stays with us. He struggles with being us and being constantly entertained or he says that his mom called and wants him home so she can give him a surprise. So, he is already learning to lie. My husband is the primary caregiver when he is at our house but sometimes my step son comes to me and will stay by my side begging for attention, so I will give it to him. Am I right? What else can I do?