How to setup a SPF record to help fight SPAM
Solution 1:
There is an article on Google Apps help about this.
http://www.google.com/support/a/bin/answer.py?hl=en&answer=33786
All you need to do is add that TXT record and you're set. I don't know what you mean by "fight SPAM", as all this does is authenticate that the e-mail you are sending is not spoofed, so all it will do is help you get your e-mail in someone else's inbox instead of their spambox, if that is currently the case.
Solution 2:
You can use the Microsoft Sender ID Framework SPF Record Wizard to generate SPF record.
Solution 3:
SPF doesn't prevent spam from being sent to you, it only helps ensure that no one sends spam as you. Also, when bulk mailing, some mail services (hotmail, google, yahoo) pretty much require the sender has an SPF record or else the mail will likely end up in junk mail folders. Also look into setting up a DomainKey record, as this is Microsoft's way of accomplishing almost the same thing.