My advice is to find a local professional or networking organization, and start taking an active role. I have been particularly impressed with the individuals I have met who have organized, or who have taken on additional responsibilities for, groups like the Philadelphia Standards Organization, WordCamp Birmingham, and TechMixer University. These three organizations/events really display a broad range: from small, informal meetings with occasional lectures, to large conferences with 400+ participants and corporate sponsors.

If there aren’t any organizations that suit your profession, consider starting an orgnaization. It can be as simple as setting up monthly meetings at a coffee house or even a (preferably quiet) bar. Sites like Meetup.com can help you organize a group, Upcoming can help you publicize events, Eventbrite can help you manage registration (if you can accommodate a limited number of guests), and Google Groups can provide an online discussion forum to keep communication open between meetings.

Leadership roles are not restricted to your profession: you can pick up leadership experience anywhere. I know a lot of people who have gained valuable experience through religious groups or social organizations. A couple other examples from my experience:

• In 1998, a friend and I organized Quick Novel, an event at which a handful of authors collaborated to produce a novel in a single day. Although the result was not high literature, the ability to pull it off at all required organization, team-building, scheduling, and finding and securing a location with sufficient computer workstations for all the authors.
• In 2002, 2 friends of mine organized an art show at a local gallery space, titled Immedia Des Refuses. Again, my friends had to secure a space, curate the show, publicize the event, and provide hors d’oeuvres and beverages. The event was a great success, thanks to their great efforts, and as a result they were seen as leaders in the local art community.
• Just last week, the neighborhood association in my community sponsored a showing of The Little Shop of Horrors in a local park. The organizers had to secure permits, raise funds, contract with a company that could provide the required screen, projection equipment, and sound system, publicize the event.

I think 2 things become clear from these examples:

1. You can develop your leadership skills in almost any area you can imagine
2. Leadership is primarily initiative and effort, with a strong dose of coalition-building

Think about it from an employer’s perspective: do you want to hire a complacent employee who waits to follow others into action, or do you want someone dynamic who will initiate action?