And here’s how not to do it…
Don’t make the text you want them to type into the field SELECTABLE WITH A MOUSE. For the love of God. A guy just told me he saw a developer show off his new rock solid CAPTCHA implementation. He demo’d it by highlighting the CAPTCHA text, copying it, and pasting it into the field.
Devs don’t need security training, they need to get out more. How about reading some technology news? How about paying attention to the IT world as a whole? Making CAPTCHA text selectable? In. Sane.