My toddler wakes up at nite?

my 19 month toddler sleeps in our room only in his cot. he will sleep ok but then during nite he wakes uo so many times. at first i wont wake up to c if he will sleep by himself but he doesnt and then i have to wale up n tell him to sleep, he doesnt take much long to sleep after that but still its very tiring to wake up every hour or so........wat can i do so that he sleeps all nite...pls help