The most important thing is to show progress. Agile/Scrum/XP are much-maligned these days, and with some good reason, but the one thing they do very well is to

The most important thing is to show progress. Agile/Scrum/XP are much-maligned these days, and with some good reason, but the one thing they do very well is to get you on a cadence of delivering working, demo-able code on a regular interval. Every situation is different, but in my experience being able to sit in front of stakeholders every couple of weeks and show them what you've just built, talk about what you're building next, and explaining anything that might impact that, gives people a lot more confidence in a team. In my experience, what scares stakeholders is when the nerds disappear for months at a time with only hand-wavey status reports to show how they're doing. Get them in a room on a regular basis, and demo what you've built. If you can't get them all in a room, record screencasts and share them, or demo over Skype/Hangouts/etc.