The technical question I have start easy and get progressively harder as we go deeper. I think thats a good strategy - everyone I interview should be able to get started, even if they're feeling anxious, and if they cannot then we can both save time.
Then as it gets harder the interviewee is familiar with it, and I find that often people with less CS experience are still able to work through it even though they don't know the terminology. And we have a grading based on how much hinting we needed to give, which is very helpful guidance to me as an interviewer.
The problem I usually pose is a slimmed down version of one I actually tackled, so it doesn't feel like an arbitrary test that has no real application. Which again, very helpful for when I need to write a rejection email, as I can say where the candidate didn't meet expectations, which often seems appreciated. We're encouraged to reject during the interview if it's obviously not going well, which I've done but I do find very hard.