Baby sleeping through the night

Sometimes my LO sleeps through the night but most nights he doesn’t... not sure what I do differently to make him sleep all night... I tried putting him to bed later ... feeding him more ounces of milk during the day .. it’s always a hit or miss and it is sooooo frustrating ! (He does put himself to sleep when I lay him in his crib drowsy but awake)... who else is in the same boat? What has worked for you??