For example, someone wants you to take a look at what they're working on to help them understand what problems may exist with that thing.

Assuming they're not some sort of family member, it's essentially a shit test, no? Do ya'll have any go-to responses to turning stuff down in business?

"No" is ofc a common one, but politically that's not the best IMO. Are there any better ones?

btw, this isn't in one office, generally speaking, this is the diplomacy that occurs across colleagues within an industry.