I started by reading the tweets from the few people I followed, but most of them lived in the same area as me and I wanted to see what was possible on a bigger level. So I started looking at the people writing the tweets that were getting ReTweeted (RT). I again looked at profiles and recent tweets to see if I felt they might add value to my "Twitter time." Most of those people fit my "requirements" for being followed. If I follow someone on Twitter for a while and then decide I am not finding their tweets very useful (especially if they have a lot of 4square), then I just unfollow them (this is my personal opinion).
I also find more people to follow by sometimes participating in things like edchat. If someone asks a question that I respond to, I also look at the other people who have responded to find more people to possibly follow. The same goes with people who use certain hashtags (that is when you "tag" you tweet with a number sign and certain letters ex. #wsfcs). I also don't necessarily follow everyone who follows me.
Now, at first I did not think I had a PLN since that was, in my mind, for people who had been on twitter longer and connected with more people. I have come to understand that for me, anyone who contributes to my learning is a part of my Personal Learning Network, whether online or not, but Twitter has allowed me to learn about so many things from so many different people.
I am thankful for all that learning and for all those people! :)