How Do I Identify the 7 Wastes?

You could flowchart the process and definitely include those who participate in the process.  You’ll be able to identify bottlenecks and inconsistencies as well as areas prone to errors. Also, when errors do occur, you could dig to find the root cause.  Waste could also include providing more information than what is needed.  I’m in an office setting (rather than production) and we had the person who calculated the commissions (me!) provide an entire worksheet to the payroll person to use to enter commissions, but really only one column was needed, and the wrong column was used by mistake – luckily, it wasn’t a big difference.  That was an easy fix, but it’s necessary to investigate the errors while keeping the focus on the process, not the person; once everyone feels that way, they’ll be comfortable letting you know where the wastes are!

Observation is an excellent tool. I like to train those in the process what the seven wastes are then “Go to Gemba” and let them point it out, take ownership, and then let them eliminate or reduce the waste.
For upper management I try and employ value stream maps. Its visual, they can ask questions and see the nonvalue waste in the process.