There are so many ways to get professional development, and I make use of as many of them as possible. For the very literal, there is the popular conference. Conferences can be found all over the globe and on myriad topics from The University of Hertfordshire's Open Graves, Open Minds: "The Company of Wolves': Sociality, Animality, and Subjectivity in Literary and Cultural Narratives--Werewolves, Shapeshifters, and Feral Humans to "WIRED & INSPIRED: The Intelligent Use of Technology in Higher Education" to the University of Roehampton's single day "Daughter of Fangdom: A Conference of Women and the Television Vampire." I just finished attending the second one in my list, and my brain is overflowing with ideas. I sat in structured sessions, took notes, and brainstormed ideas. I will take back my learning and slowly begin to implement some of the ideas.
I also enjoy the professional development that takes place between colleagues who work on studying/learning something together. For example, I once participated in a year long book group where we read books about the Millennials because we wanted to understand our students better. Books we read and discussed included Nurture Shock and Generation Me. Our discussions included ways our lessons may/may not be working for this generation's students. This professional development was small group, and we created the focus based on what our interests were and where our struggles existed. The conversations were thoughtful and paced to our needs. My attitudes toward my students changed, and I adapted my lessons to my audience.
Then, for me, there is another valuable method of gaining professional development: independent reading and studying. This can range from really good short articles to books on both pedagogy and content. I find a lot of these readings from Twitter where I follow people/organizations who tweet about education, composition, or literature. The best education ones I follow include Higher Ed Chat, Mark Barnes, Diane Ravitch, and Edudemic. For research and citation, I follow Easybib. For my literature interests, particularly gothic literature, I follow Bernice Murphy, Linnie Blake, Gothic MMU, Xavier Aldana Reyes, and Irish Gothic Journal. These readings happen at times when I have a spare few minutes--enough time to read a linked article. I try to immediately make a connection to something I'm doing in class. Many times Twitter provides a breathtaking synchronicity with what I'm working on or a quick idea for new ways to start class.
I have a lot I could say about planned or spontaneous conversations with colleagues. I find myself listening to their words long after we've parted and reflecting on my practice in light of a single tidbit or two they have generously shared with me.
I believe professional development is learning, and learning can take place in many ways.