Recently, I came across this gem from Martin Fowler's site called "It's Not Just Standing Up: Patterns for Daily Stand-up Meetings". If your stands up are starting to hit a rut, you will definitely want to read this article.
Some of my favorite parts of this article:
Good stand-ups will feel supportive. When people are knocked down every time they raise a problem, they will tend to stop raising problems. Beyond preventing removal of obstacles, a non-supportive stand-up works against team dynamics. The stand-up instead becomes a ritual that team members dread.
Regular interruption by observers is very disruptive to the delivery team by challenging the premise that the daily stand-up is primarily for the delivery team. Interruption also threatens Fifteen Minutes or Less. Enforce Pigs and Chickens.
I love this article. Absolutely recommended.