I stole this idea from dave. Basically all of the things not to do when going after an ISTJ. All of the things that would scare them away.
I'd have to say, around the time of first meeting each other:
Trying to get me to laugh a lot.
Trying to get me to smile a lot.
Asking me what's bothering me.
Telling me to loosen up.
There's more, I'll have to think about it. I'll post some later tomorrow.