Help Writing Secure Form processing script

I don't write a lot of asp code and the stuff I write is very basic and simple. I need some help writing a script that will process the output of a form (20 fields max) and send it to an email address. The code I have is very vulnerable to hacking and I've discovered after switching hosts I can't continue using it due to its vulnerability. I'd also consider hiring someone on a contract basis if necessary. Any help out there? Any books to recommend or information easily available? Tips and tricks? Anything would be appreciated.

if you're looking to hire someone, that's not really the proper forum.
if you would prefer improving the code yourself post it here and
we'll try to guide you how to make it better.