Questioned document examination involves a great many areas of expertise. Graphology, the study of handwriting to determine one's personality traits, is not handwriting analysis. True handwriting analysis involves painstaking examination of the design, shape and structure of handwriting to determine authorship of a given handwriting sample. The basic principle underlying handwriting analysis is that no two people write the exact same thing the exact same way.
Every person develops unique peculiarities and characteristics in their handwriting.
Handwriting analysis looks at letter formations, connecting strokes between the letters, upstrokes, retraces, down strokes, spacing, baseline, curves, size, distortions, hesitations and a number of other characteristics of handwriting. By examining these details and variations in a questioned sample and comparing them to a sample of known authorship, a determination can be made as the whether or not the authorship is genuine. Sign your name as you would sign a credit card receipt or some other official document. Have several friends do the same. Take a few minutes and try to forge each others signatures.