i used to be incredibly shy up until the age of about 15. what helped me was putting myself in situations where i absoloutely had to force myself to talk to people or i'd be totally alone. I changed schools twice in 4 years and that means making a whole new set of friends each time, especially as the first transition was from a bad state school to a very 'posh' private school. By doing that (and u could do it by joining a club or something) it meant i had to make new friends and it's helped me overcome my shyness massively, i'm always learning to be less shy day by day. Getting a job also helped because again, i had to talk to the public, my boss, the other staff etc. When forced, you will come through.
About knowing a little on a lotta subjects, well it's great to be eclectic. my music taste is HUGELY eclectic, but that's actually helped me make so many different friends. I have friends i go partying with who like dance music, i have friends who are all into metal hugely and they like to feel they are educating me more on the topic.
You can be a great friend, you just have to make the effort to go that little bit further when you're shy so people can see the real you