You have to know people to find the positions that aren't publicly posted.
Being shy is not an excuse, you are losing a lot of opportunities.
There is no such thing as a permanent job. Every company in every industry has some level of volatility.
Keep your LinkedIn profile updated at least yearly.
It's not about "collecting" people into your social network, it's about connecting with them as people.
At a networking event, try to make one solid new relationship.