To be brutally frank:
Google.
That is why Yellow Pages, the local and national press etc is going under.
No-one goes to the local rag or the Thomson or Yell site to look - they Google.
And if there is a local flying school that doesn't appear when you search for "(Place name) flying school", the chance of it still being in business for long.....
Finally, visit all your local flying schools on the ground and even go for a flight with one or two of them to see which fits in with your preferences. Remember, learning to fly is a big investment - not just in your money (as in buying a car would be) but also in your time (having to commit to so many lessons).
So do lots of research!
ps. What may be missing is a "Trip Advisor" for flying schools, with ratings by all types of customer, from trial lessoners to full students. But the strange thing is, most students build a rapport with their instructors and think they are gods! (maybe the CFI knows different!!)