The Three Rules of Presence was the best advice I got from the previous commander when I took command of my company.
The third rule: Look like you're leading. Show some leadership presence. Act like you expect people to follow. Portray confidence, or your team will lose confidence.
Confidence is hard when team members are more expert than you. But you're the leader because you're best at problem-solving, or organizing, or something. Trust in the talent that got you the job. Be confident in your ability to put your people in position to achieve.
The best way to stay confident: remember your role. You define the task, and then set the conditions. You don't have to lead the actual work, you just have to control the conversation, mostly by asking questions. Take a look back at my "Take Charge" post for an outline.
So take control of the conversation, guide it to a resolution, and then shift to resourcing. After the course is set, when it's time to roll your sleeves up, you can let your experts lead without losing credibility.
Bottom line: A stranger watching from a distance should be able to pick you out as the leader. If they can't tell, you're probably not leading.