Installing contact form in wordpress

Although I know (or assume) that there are plugins to add contact forms to a wordpress site, I would like to add my own code for various reasons.
I figure I can do what I did with my testimonials page, which is create it completely from scratch and just make it look like my wordpress site, and then just link to it. But I want to know how to do it within wordpress, so that, for example, I can edit my wordpress theme and have those changes carry on to my contact us form.
The page that isn't…
Installing contact form in wordpress

See original post by offthedome