One of my friends, Dougald Hine, told me once that a good friend is someone who senses when to introduce who to whom. (I take him to be talking about action, not about grammatical constructions.) Let’s parse this statement.
First of all, an introduction is not a recommendation, i.e., not a “should” statement, but a “here you are, go on, carry on” speech act. If it’s done properly, then the introduction is also a leave-taking. (No vanity, just a putting together and then getting off stage.)
Second, a good introduction has a “mood” to it. You cozy the two parties up to each other by making each look sufficiently attractive to the other. (Then hand them drinks and don’t snoop.)
Third, it’s a knack for “paring,” i.e., for sensing that P would go together with Q. “Knowing” would be too strong of a word to get a handle on this knack. “Sensing” is just about right. “I can see how it’s possible that P would go together with Q. I could see how P would be well suited for Q and vice versa. I can imagine P and Q collaborating in myriad ways together. What might P and Q talk about? I don’t know, but their conversation would undoubtedly be interesting.” The stress lies on the knack, a way of seeing that is honed through experience, associating one thing with another, and experimentation. (For the neophyte, there are lots of past oopses.)
Fourth, there is the timeliness to the act. Certain times may be too early and others too late. The remedy for the “too early” is patience. The tonic for the “too late” is Three Stooges. (I jest.)
Fifth, the introducer needs to be able to forget. Provided he hasn’t exercised poor judgment and put together two nasty persons, his responsibility ends with the introduction. So do his expectations. What happens from here on out is anyone’s best guess. He needn’t feel ashamed or be disappointed if “nothing happens” for P and Q. It’s possible that “nothing happening” for P and Q is the lesson for P and Q. (Zen me!)
I’ve no idea what learning to be a better introducer would entail, and I can’t make much of the idea that one could be taught to be a good introducer. My guess is that, with time, the introducer-in-the-making develops rules of thumb and may even learn to be more cautious. (And isn’t growing old about getting the knack for not shooting from the hip?)