L.G.
a book that always worked for me (Good Night, Sleep Tight - Kim West) says, that they should have 11 hours uninterrupted sleep at night with 3 1/2 hour of nap time spread over 2-3 naps.
It depends on the child, but one of the best things i ever learned was "sleep begets sleep." this means that the better your child sleeps during the day, the better he/she will sleep at night. it is NOT TRUE that keeping kids up during the day or later at night will wear them out and help them sleep better, and this has definitely been true for my daughter.
i also learned at one point that my daughter was sleeping too long in the morning (2 hours or more) and then resisting a nap in the afternoon. the afternoon nap should be the longer one, because it will be the one they keep when they are older.
also a good idea to make sure they don't sleep for more than 3 hours at a time (especially when a little older) and that they wake 2-3 hour before bed time.
finally, babies do better when naps are consistent. by this age, they are ready to go down for a nap at a certain time, and will not just fall asleep here and there as when they were newborns.