To create a list, log into your Twitter account, and on the right sidebar you should see an area called Lists with a link to create a New List. You can even set the list to be Public and have anyone subscribe to it, or Private, and only be able to access the list.
I personally find it helpful when it comes to finding industry leaders, as it is beneficial to follow the leaders in social media or the leaders in SEO. A way to see if you are part of a list is to log into your Twitter account and right next to your Following list, you can see if you are part of any lists.
A great site to find Twitter lists categorized by different tags such as bloggers, celebrities, food, health, politics and technology is Listorious.com. You can submit your lists for everyone to see and follow as well.
