I find that when I approach sets that are just "chillin" things work out a lot better, or when I see a set that looks like they can use a little entertainment. The sets that are in a deep conversation with each other seem to shut out the world around them, I was working on day game with one of my friends at ASU and when he opened a set in conversation they told him "You know what we don't car so why don't you just keep on walking", it was a harsh crash and burn. Well of course these things will happen sooner or later and it's no big deal, I just rather have it happen less often.
Now that I think more of it, the set that I opened in a Starbucks was talking about some drama or relationship issues, something to those lines, I only caught the few words they spoke before I interrupted. Their position was in a corner of the shop sitting down, no where to really lock in either. My opener was the one I made "White Lies", and that got them interested in what I was talking about, the only problem I had was my inability to escalate the energy levels. Maybe it's because they were in a shitty mood when I approached so it takes a while to transition out of it, idk. But yeah there will always be those elements out of my control the things that happened before I came.