Expenses seem to breed and need to be sprayed regularly if they are to be kept under control. The problem in reviewing them is that the way accountants present them is not helpful and they need to be looked at in a different way that makes review easier.
What I do is to reformat them in descending value and then, starting at the top, take one or two a month, isolate them and ask the following questions about each one.
Why does this expense exist? Why do we need it? Is it necessary in its present form? Is there another way to accomplish this? How can we reduce it? Can we outsource it? Can we turn it into a profit center?
There are probably more questions and different ones appropriate in different industries. Just take one expense a month and hold it up to the light, and the return will be up to three times as great as a similar investment of time in sales.