Even small, taken-for-granted words can have a strong influence on the pedagogical effect of a writing conference. In this study, we examined how experienced and trained writing center tutors' use of the discourse marker so helped them to connect ideas and to manage their conferences with students. We examined the extent to which tutors' use of six types of so varied according to the English L1 (EL1)/English L2 (EL2) status of their interlocutor. We studied 26 conferences: 13 involved eight tutors working with 13 EL1 students, and 13 conferences involved eight tutors working with 13 EL2 students. We found that conclusion/result so occurred most frequently in tutors' conferences with EL1 and EL2 students and that prompt so was the only type that exhibited a significant difference in frequency of occurrence between the two groups, occurring more frequently in tutors' talk with EL1 students. We focused our qualitative analysis on prompt so, finding that it served two main purposes. We argue that examining discourse marker so generates implications for tutor training and shows the importance of paying attention to the small, seemingly unimportant words that tutors use.