checking info before putting into database

Hi Guys, Just need peoples thoughts on the following when putting information into a database (the information is from text put into form feilds by users), I know I have to run checks for security and integrity issues but I am trying to work out what checks I should run as standard. At the moment I am running these checks on all vars that are going into the database. $f_name = trim($f_name); // I use this to remove any whitespace $f_name = addslashes($f_name); // I use this to protext my self from -'s- situations $f_name = strip_tags($f_name); // I use this to remove any PHP and HTML tags I use checks above as standard checks that I do to make sure things are safer. Also is there any quicker way of doing it that anyone has developed rather than writing the above for each variable. Maybe creating an array and looping through the array, while doing that running these standard checks on the variables. Thanks for any info, thoughts you can provide. Scott.