Before you learn how to factorise quadratic expressions, you will need a supply of them (and their answers). This is because constant practice can make you an accomplished 'factoriser,' and factorising is an essential skill in algebra and graphing. Avoiding this practice is a bit like saying that you want to become a good sailor, surf skier, sail boarder or surfer, but you will not invest time in learning to swim.
During the last decade or so I have developed an Excel Workbook as a resource for my students. It produces a huge variety of expressions for you to practise on. The quadratic expressions and equations are randomly generated, literally at the touch of a button (the F9 key). Also, the answers are provided on the same sheet! You can even change the level of difficulty at will.
Teachers, feel free to provide a copy of this to each of your students. It will help them develop their skills quickly. You might even consider using it in class. Parents and students are free to use and distribute it freely. The only condition is that you understand that I retain copyright (ownership) of the workbook and I give you permission to distribute freely, but not to sell it in any way.
The workbook contains no macros and is virus free. You may obtain it here.
If you find this workbook useful (or if you have suggestions for improvements), please leave a comment for me. Thank you.