The mindset that makes your missions experience great or just average is the mindset of being a curator. This is infinitely more than just a 'leader' or a 'tour guide' or a 'chaperone' although you can use those titles, except for the last one. Instead, you become an anthropologist, a futurist and a talk show host all at once.
You help your students understand the past and present - why does this group of people function like it does, what are the predominant values of this city, what elements of the past inform why people act this way in the present.
You envision a path for the future - what do my students learn from this and how does that affect their behavior 5 or 50 years from now, what latent dreams and passions are erupted out of this experience, you say to them, "You know, you could do this too."
You ask a lot of pointed, intentional questions that form a bridge between where your students are, where they could be and how hosts, co-workers and people with the same calling help your students get there. You've done a lot of research on the people you are working with before you landed in-country, so that you can have an intelligent discussion with them about what they actually do. You interject, stop here and there to chat about this or that, keep a running list of notes in your pocket for discussion later.
Most mission experiences are good - people get there and back, they serve somebody and the students are exposed to another culture. Being a curator takes this experience and turns it into a time when your students learned to peel back elements of a culture and deduce significance, they envisioned a future that was bigger than themselves, and they heard deep stories of calling from people they worked side by side with.
Curation is catalytic leadership at its best. You know, you could do this too.