How To Buy a Doorknob

There are several things to consider before you select a doorknob.

Think about where you will be installing the doorknob. Interior doors don't typically need keyed locks, for instance.
Decide what you prefer - a standard round knob shape? A thumb latch? A lever-type knob?
Consider who will be using the doorknob. Children, handicapped people, and persons with full hands will appreciate a lever-type knob that is easier to open.
Install passage knobs on closets and other non-locking interior doors.
Put a privacy lock on bathroom doors and maybe on bedroom doors. This is the type that locks from one side with a button or thumb turn. It can be unlocked by poking a toothpick or similar object through the hole on the other side.
Use keyed locking doorknobs on all exterior doors.