You're right. Observing the little details is a good strategy because they do reflect the overall hygiene standards of the place. Staff and kitchen hygiene is a big give away, as you mentioned. Sometimes, it's the little things like a tidy chef or prompt waiting staff that can make a positive first impression.
And yes, I've been in situations where the place was spic and span, thanks to a recent renovation or new management taking over, which left a good first impression (and hopefully, it's not just a front)! It's definitely tricky to gauge sometimes.