Your ability to “win friends and influence people” will only be as good as your language skills. The best way to hone them is to read a lot, and read some more. Novels, histories, science-fiction — it doesn't matter, just read!
Besides English and mathematics, there are two other fields that you should keep up as long as you can, even if you don't do them as formal subjects. These are music, the language of the emotions, and sport, the language of the body.
There is no substitute for raw knowledge, even in the age of internet search. After all, there is no use learning to collaborate if you don't have anything distinctive to contribute.
Interesting read! @Kpaxs