As a nanny fro 17+ years and a mom of a 14 month old my best advice is this...
Babies at that age will need to sleep again after 3 hours of wake time. Some, like mine, need help to do this.
At the 2.45 hour mark of them being awake begin to settle down and relax. Cuddle, nurse, rock, read a book etc. Then put him in his bed really drowsy and "blinky" but not completely asleep. Pat him on his back until he falls asleep in the bed. This will help him get used to falling asleep in his bed and not on you.
It will of course take several months (possibly) to establish a "perfect" routine. The schedule and sleep time routine will greatly help. He will eventually fall into a regular sleep pattern with longer periods of sleep. He will know what to expect and when to expect it and not be confused or surprised by what is happening next.
*if your baby is on a feeding schedule of every 3 hours this will help coordinate naps. If they nurse on demand you might need to top them off before nap time to keep them from hunger waking.
Here is a sample schedule we tried to stick to.
9am wake and nurse
12pm nurse and nap (1 1/2 to 2 hours)
3pm nurse
5pm nap
6pm nurse
9pm nurse and down for the night
If my baby woke early from a nap I would attempt to get him back down. Sometimes he just needed his paci or I would pat him for a minute. More often than not this would work. I would also wake him sometimes to keep him on schedule.
Just keep in mind that every baby is different and you have to take their lead sometimes. As they grow their needs will differ. Enjoy every wakeful second because before you know it he will be running around that house!