Meeting my Boyfriend's Baby Mama/Becoming a "Step Mom"

in about a month I'll be taking a 1,300 mile road trip with my boyfriend to go pick up his son and meet his family and the baby mama. I'll be babysitting his son full time this summer so that my boyfriend can afford to have his son living with him, and I'm super excited to finally get to meet his little guy! but I'm very nervous to meet the baby mama. I want her to know I respect whatever relationship she has left with my boyfriend, and I want her to like and trust me and not just tolerate me. does anyone have any advice on how to go about this situation? also any advice from step mom's would be appreciated because I've never been in a position like this before and would greatly appreciate advice on anything step-child related. obviously I'll talk to my boyfriend about discipline and other stuff that he wants me to do, but how do I become a good "step parent" sorta figure for this little boy?