1. Start on a high note, take the team out to lunch / dinner and start to get to know them.
2. Don't force any changes, they will likely resist and you'll lose any budding support. Forcing a code review workflow is likely to demoralize them, and will be perceived to be slowing down dev that's already behind.
3. Work longer hours than anyone. You need to earn their respect, being seen to work insane hours is the fastest way to prove your commitment.
4. Do one on one interviews with everyone, and listen listen listen. They know what's going wrong.
5. Strive for consensus, and become their champion in relation to upper management.
6. Never denigrate any member of the team, even if they are exceedingly incompetent. Work with them to assign tasks they can complete.
7. Heap praise on every good process and success you see.
8. Never claim any credit for yourself, ever. Make sure the CEO understands this, and doesn't praise anything you do in front of them.