I want to remove "Search for" text from search form in TwentyTwelve, to wrap in in a div for styling, and probably to play with php a bit – and I'd appreciate some advice on how to do that best.
My "sub-questions within a question":
1) Where is the main search function is located?
2) Should I create a separate custom file, add code to functions.php - or is it okay in this case to just edit the original search function?
Thank you in advance for your help!