Tips on print to screen debugging

I have always had problems in cutting and pasting new forms off old ones. Often the problem is in the communication that makes the form allow repliers to view results on screen. This is good to do with opinion polls to start discussions. I have a *terrible* time locating the source of the error. Do experienced .php users have a method for finding errors in the print to screen? I will send the culprit .php file to anybody who is willing to look it over. Thanks, Gloria McMillan