Use astrology. Each astrological sign includes a profile of personality you can choose from, such as the indecisive Libra (so much like me), or the temper-ridden Taurus. Even Chinese astrology creates pre-made personalities, and even how the personalities mix with one another.
Use people you know. Every person consists of unique personalities that makes them one-of-a-kind. Pick a few qualities that stand out, from appearances such as the bushy brows or thin lips, to the distinct profiles of temperament, skills, and even hobbies.
Use historical figures. Change a few things around to make them your own characters, but consider such vibrant people such as King Henry VIII or Catherine the Great.
Use personality tests. These can often be fun to figure out where you are with being labeled. Go through such tests and change the answers to see what type of personalities you can come up with.
What do you do to make up characters? Imagination only? Influences from Life? Post in comments.