SSL is the way to go. We can give you tips here, but I HIGHLY recommend you spend some (ok - a lot) quality time researching SSL, how to install it and how to use it. You'll need to know what web server you're using and follow its directions for installing the certificate.
And remember, handle the credit card number as if its your own and handle the number as little as possible (aka: don't be storing it anywhere or sending it off in an email).
