I think people normally use the Contact Form 7 plugin for their WP contact forms. It’s pretty good, but I think I’d recommend Dagon Secure Form Mailer.

I prefer the way it allows you to change settings by editing separate files: you can style your forms in a CSS file and even change form labels and button text by editing the language files. This keeps things simple and consistent.

It also offers more file uploading options: crucially, you can opt to upload files to your WP install rather than have them emailed.

Finally, I find it a lot more reliable, especially when it comes to setting required fields.