My son is 21mo and he was never a great sleeper. But at 10 months he got it. Then at 15 month, he started waking up or expecting us to make him fall asleep. He used to wake up at 2 and get up at 6.30. One night I said 'Enough!'. Let's let him cry.
He cried for an hour, the following day, 30min, the next day, 15 and like that. Now he sleeps through without a problem. Mind you, we never entered the room once he started crying unless we heard there was a problem. I think that the more you go in, the crazier they get.
Last night he refused to go to bed. I gave him a hug and he cried, then slept. Now, right now, while I'm typing, he's crying because he's not ready to sleep but I know that if he doesn't, he will be knackered the rest of the afternoon. So, there he is crying. Oh, now he's stopped. He's tired.
Some parents don't do a crying method - certainly I was one of those until I went mad! Now, he sleeps wonderfully - well, until yesterday. But whenever he refuses to nap or go to bed, I let him cry. I may sound crazy but it has to be done sometimes.
Good luck!