We have a 19.5 month old and we got the same issue. We got him to sleep a couple months ago but had to let his grandparents keep him one night which totally screwed up his sleep and we were 3 steps back from step one. heh.
One of the things we found out was that the sleep environment (since he sleeps in our room and we just rearranged everything) was causing him to wake up more often.
We are back to 3 times per night. Our pediatricians assistant said try a sippy cup instead of a bottle and we found out it's a comfort thing. My husband will start to feed him a bottle yet go less and less w/ the water.
My suggestion- Wait till your child does escalate the situation- many children are active in their sleep and we accidentally wake them up if we immediately respond and not let them settle down for themselves. After you realize that sh e is in fact awake and getting a bit more upset go to her. (We use the easy but longer method of help since we hate the 'cry it out method') But we have a rule- take whatever works but DO NOT take our child out of the crib. They get used to staying in the crib -after some sleepless nights- and allowing comfort in the crib.
Once that becomes a consistent knowledge to your child go to the next step of giving little bit less help. We stay with our child less and less, maybe just patting him instead of hugging him IN the crib. Then they start realizing they require less and less help going back to sleep.
We are down to giving a bottle 3 times a night to him. (Far from where we started. heh. Remember all your family successes to make it a forward process) Now we are going back to what worked last time. A 3oz bottle of water. Then 2oz after that. Then 1oz after he adjusts. Its a longer process, but seems more 'humane' to all of us.
Some good books are "Happiest Toddler on the block", and "The no-cry sleep solution". YOu can get them from the local library to see if a solution works for you."Happiest Baby on the block" might have some tips, but it's been a while since we used that books benefits.
-steffi