Few ways to gain leadership credibility:

1. Do the things other people don't want to (that's a big one in software industry).
2. Change your default way of thinking so that you consider everything to be your responsibility until it is otherwise delegated. That doesn't mean you do everything. That means you don't ignore something because "it isn't your job". THIS IS KEY.  Leadership = ownership.
3. Do what you can to remove roadblocks that are keeping others from progressing in their tasks.
4. Know your domain be it IT, software dev., networking, enterprise engineering, etc.
5. Complement or praise your peers. Giving praise is a sign of authority. It also makes people want you to be their leader.

On the other hand, leading does not mean:

1. You make all the decisions.
2. You force your opinion on the team.
3. You tell people what to do.