Processing Form Input and MySQL - Best Practices?

I was hoping someone could point me to an article about some recommended best practices with respect to taking form data (entered by a user), storing it in MySQL, extracting it again and displaying it back on a web page. In particular, I want to make sure someone isn't entering data that could potentially be harmful when it is displayed however I also want to allow links stored in the database to be displayed correctly (as a valid link) when displayed on a web page. Thanks, Mike - mike_walsh at mindspring dot com