Ask him the trick question: "So what will you be teaching me?"
If he answers right away with a fixed curriculum of sorts, then he may not be really after your improvement, just your cash. It's a trick question. A teacher won't be able to know what to teach until he has tested your current skills. The right answer would of course be: "OK play me something"
OTOH, A lesson or two in, the teacher should not be asking you "okay, what do you want to learn next."
The teacher should spend the first lesson or two finding out what skills you currently have, and what you want to play. After that, they should be teaching you what you need to learn to get there.
I took some guitar lessons at a local guitar shop. They were terrible. Look for these warning signs.
1. Teacher repeatedly asked me "what do you want to work on today?" - If I knew what I needed to work on, I wouldn't be taking lessons.
2. Teacher constantly told me "you should bring your accoustic next class" - I was quite clear that I wanted to play rock, punk, and ska, and that I would be using my electric.
3. Teacher would constantly introduce a new practice drill, and then follow with a full minute of uninspired wanking. (Usually the same unrelated boxed in pseudo-solo,) - He's goofing off on my time, and if it's related at all, it's only by coincidence. "Someday you'll be able to play like this. wank wank wank"
4. Teacher had no interest in the styles of music I wanted to learn, but took my money anyways. - I'm not into flamenco. 4 lessons with this guy, and nothing even resembling rock.
5. Teacher constantly trying to sell you stuff. - If I wanted to learn from a book, I would have bought a book. I'm not saying that books can't be valuable reference as well, but you shouldn't be expected to buy a book in order to have something to work on in your lessons.
IMO In your first lesson any decent teacher should be asking you "What kinds of music do you want to play?", "Who are a couple artists groups that you like, and see as an influence?". That should probably be followed up by "Play me some bass parts that you have learned recently."(unless you're an absolute beginner)
I think most people will likely have to bounce around a bit before they get a teacher who really clicks.
Don't feel like you have to stick with the first teacher you hire.
I'd recommend against buying into any lesson "packages" until you've had at least a few individual lessons.
The teacher I have now, I got a single lesson. It went well, so I paid for 6 more. This way I'm there long enough to see if I like the direction I'm heading. If so, I'll buy some more. If it turns into a waste of time, I'm only out a few wasted lessons, and I can find someone else.
-Nick