one of the things they don't touch on in that article is whether one should fulfill their fantasies or not. I saw a shrink back in the early 90's and one thing he said was the problem with acting out your fantasies, is that they no longer are fantasies and you have to come up with new ones. And that can lead down a very dangerous path. Another thing about living out a fantasy is that rarely do they live up to your expectations.
For example: I've had 2 threesomes and neither was anything to write home about. One was totally faked by 2 ee escorts and the other, well, things just didn't fly very well. Now I bet a natural threesome would be better, and hopefully will experience it one day.
Anyhow, as to who to fantasize about during sex. I've been lucky. All the women I've been with have been hot enough that I don't have to think about anyone else. One was SO hot I actually had to think of things like: the flu, sore back etc to keep from cumming too soon lol....