Even a new manager has a reputation to uphold in front of their employees. If you have some sort of criticism to deliver, ensure that it is done in private and not in front of other employees. Confronting the manager in public can not only embarrass them, but it can make you lose respect from the surrounding employees. This can also make the manager angry and defensive, which can counteract the purpose of trying to offer help or create a solution.
However, praise and positive feedback should be delivered in public and among other employees because it can be a positive influence and encouragement to others. It recognises hard work and success, and it shows that hard work can be recognised and applauded. The manager will get a sense of accomplishment from being praised for a job well done and will be more likely to perform at high levels.