Figuring out who the cool people are. (Similarly, figuring out what the cool ideas are.) Being able to identify cool people has made my life significantly more awesome than it otherwise would have been, and led me to learn skills like guitar, chess, hiking, rationality subskills and so on that I wouldn't have bothered to or been able to develop on my own. It made high school an amazing experience. It got me laid by hot chicks. It led me to lots of good music. It lets me easily distinguish between meh philosophers/authors/artists and cool philosophers/authors/artists, so I don't waste time. It also alerts me to the existence of communities like LessWrong and the Singularity Institute and to cool intellectual cultures or academic fields like algorithmic information/probability theory (and thus universal AI) and Bayesian computational cognitive science. It lets me know which AI approaches are going nowhere and which might actually be dangerous. It also allows me to feel justified in ignoring people who don't think I'm cool, since I have a good sense for coolness and I think I'm cool, and if others don't have a good sense for coolness then they probably aren't cool and won't become cool—this obviously isn't a perfect test but it's useful.
It's not necessary to do so, but once you figure out who the cool people are it is very helpful to befriend them or get into correspondence with them. Since the age of 15 or so I've identified the coolest person in my community and then tried to establish a friendship where I'm slightly lower status than them, such that it's easy/natural for them to teach me lots of stuff. (And the coolest people always have cool friends; becoming best friends with the Homecoming King in high school allowed me to meet all kinds of cool people who I otherwise wouldn't have realized were cool. If I were attending university then befriending a really popular (ideally intellectual) person would be one of my top priorities.) I am extremely happy with how well this strategy has worked. Of course, it wouldn't have worked if I didn't have high CHA, but if you can train charisma then training the "recognizing cool people" skill would give you lots of added benefits. I think it's related to general "taste" as in aesthetic taste, so cultivating your sense of aesthetics might also benefit your coolness-recognizing algorithms. I'm also not sure that general aesthetic taste is trainable but I think it is.
What do you mean by "cool"? If you're including LW and the homecoming king in the same concept, well, that seems very broad.
So, transferable skills: skills that, upon improvement, increase your ability in other areas (and also improve other, higher-level skills).
A basic example would be reading/writing. Knowing how to read and write allows one to access a huge amount of other skills and resources which are otherwise unavailable. A less obvious example would be clear speech (enunciation). Ability to speak clearly improves one's prospects in a lot of different areas (e.g. professional advancement, dating, etc.).
I'm looking for additional examples. Which skills did you find to be most transferable? Did you become proficient in X, and then found this helped you in many other areas of your life? Please share.
(I tried to find whether this was discussed before, and failed; if it was, I would appreciate the link.)