This is an important question. There are several important considerations.
First, baby and child seats should be in the back seat of the car. The airbags, which are standard in many cars in the front seats can hurt a baby.
Second, for the first two years of the child, the seat should be rear facing. Or better yet, until the child outgrows the child seat, the seat should be rear facing. The rationale for this is as follows. When there is a crash in the front of the car, the crash is dispersed on the whole back of the child. This limits injuries and front crashes are more common than back ones.
Third, the safest place in the car is behind the driver's seat. Hence, the child should be in a child seat behind the driver.