Confused about which function to use with forms/database

Hi, I have forms that retrieve date from mysql databases and send (for storage) data to same databases. I note many functions to make sure that the data is correct in appearance when it comes to special characters. addslashes() stripslashes() htmlspecialchars() htmlentities() get_html_translation_table(HTML_ENTITIES) I've read the documentation but am still confused about what to use when. When passing data from forms to database, which do I use? When retrieving data from database to display in forms, which do I use? Thanks, Don