P.N.
My DD started waking every 1.5-2 hours around 8 or 9 months. It lasted a while (seemed forever at the time) then all of a sudden she stopped doing it. I don't believe in "sleep training" and I would never CIO at all. It is absolutely normal for babies to wake during the night. I have found that my DD has gone through different phases where she went down fine, slept fine then suddenly was waking. None of this changed based on any techniques I tried, she slept better when she was ready.
All that said, I do recommend Elizabeth Pantley's "The No-Cry Sleep Solution." She has a lot of techniques for babies pre-8 mos and post. Could be helpful. She based her techniques on parenting several children. Good luck.