Installing pre hung doors.
O'mike is right, but I should have mentioned that I prefer to use something like a GRK trim head screw for securing jambs (not a big gold phillips screw)- the heads are almost as small as a finish nail, but being a screw, allows you to adjust the jamb by turning in or out slightly and snug up the jamb to the shims. Just my personal preference- there are a lot of ways to do it. I like my door jambs to be as rigid as possible so everything doesn't shake when you close the door.
Definitely replace a top hinge screw with a longer one to take the weight of the hanging door.