A good way to meet new people in politics is to run a recruitment table for your campaign or organization at a local conference. These conferences are often day-long affairs, and can really put a cramp in your social life or other plans you may have had.
But they're good to attend, because through it you can meet entirely new people.
And it's important to understand what you're going for:
1) You obviously want to make a good impression
2) You want to get their contact information
3) You want to learn about why they're unique or valuable, what they "do"
4) You want to give your contact information
5) And you want to tell them what you're doing that's unique and valuable
Don't be afraid to go up to people. It's socially awkward, sure, but it's awkward for everyone.
And in keeping with the advice in the book, it's also important for you to have:
1) Plenty of business cards to hand out
2) Your personal 10 second sales pitch thought out
People you meet at events like this can be a potential future campaign to work on, a source of potential donors, and opportunities all around.
I once went to a conference, I was very discouraged and went anyway. I felt like I met no one useful, but one participant, just one, gave me the name of another student in a town in another part of the state. It would have been easy for me to disregard the referral or throw it away. But I followed up on it, and the person they directed me to became a very important contact, became a key volunteer at my job, and also became a great friend.
Around that same time, I went to another conference and made a presentation, again with a certain degree of reluctance. The presentation lead to a great political job offer less than three months later, and I had no way of knowing the connection until they made the offer.
The opportunities at these conferences and events are never immediately obvious. And you want to approach them with your best foot forward. Make sure you have your business cards and that you look sharp. Working thankless tables and attending conferences can pay off unseen dividends over the long term.