Things that put me at ease when I'm with other 'S's:
Having common interests, and talking about them.
DOING shared interests together.
Shared sense of humor.
Shared sense of values. (Don't fake these, though. It's ok if our values differ, but it's good idea to defer any value conversations until we know each other better if you goal is to build comfort.)
Oddly enough, sharing your problems with us if we give you a window... which as an INFP I will constantly be doing. My empathy is one of my greatest gifts, and if someone shares themselves with me, and let's me empathize with them, I relate to them.