The first question is, "Who is 'we' and why do we need to know?" Context matters a lot here.
In fact, it's practically all that matters. In some situations yes, IQ is what you actually want to know. In other situations, no, you care more about other things.
I've never heard of anyone saying "I thought that person was really intelligent, but they turned out not to be", and when there are scandals about people with fake credentials, they don't seem to come from people with fake credentials making mistakes-- instead, someone checks the history.
It seems to me that you can find out a lot about people's intelligence by talking with them a little, though I've underestimated people who were bright enough but didn't present as intellectual.
The real problems are with identifying conscientiousness, benevolence, and loyalty-- that's where the unpleasant surprises show up.