How can I ensure that my code, program, or software is functional and secure?
Using functional testing, Unit testing, funtional testing, etc., doing security assessments and code reviews, input validation, documenting code, and regular code reviews are all great ways to ensure that everything is secure and functional.
How do I interpret user needs and incorporate them into a program?
First you need to make sure that you gather as much information from the client as possible and keep the client up to date throughout the entire process. Then we should proritize requirements on their importance to the client as well as create functional and non-functional requirements. You should do contant reviews and make sure that what is happening is aligning with the clients idea of what they want it to be.
How do I approach designing software?
I first like to make sure that I understand all the requirements. I feel like this is a big part of doing any kind of project. You need to know what you need to do before you can even begin. If you start without any plan then it all can become jumbled together and not meld together how you eventually want. I also like to get what I want wrote out on either paper or in a document to get my ideas out and then I can try and piece together what I am thinking.