Sorry, I laughed.
Hm... from my perspective, it takes patience and persistance to get close to me. I'm constantly observing, taking mental notes, never initiating social exchanges. Just be your genuine self, I know, I tend to see right through people. Oh, and unless we share common interests, there is no connection. Most people never learn anything about me, besides my personality. I get along with almost anyone though, so my aquantances are from everywhere.
If you tell me a joke, I'll laugh, even if I don't get it. I'm always laughing when I get the chance (my "fake" ones sound genuine), just don't ask me to explain your joke. It defeats the purpose of avoiding awkwardness (and annoys me, "why the hell do you need an explanation? Move on", said through a smile and chuckle). Sometimes I won't laugh (bad mood perhaps), don't take offense.
Smiling at me, probably wouldn't get much of a response (unless we've established friendship). I'd only think, "why is this person smiling at me?" and by time I've decided to smile back it's too late so I don't bother.
My advice to you, relax. Don't read into an ISTP so much, focus on the way you present yourself (stop being so inconsistent, stop strategizing, stop trying to please them, just be yourself). ISTPs are not judging you, and you're not gonna fool them.