SPF is pretty simple to set up, you just need to add an entry into your DNS that specifies which IPs are authorized senders for your domain. Go to
http://www.openspf.org/ and start the setup wizard.
Sender ID is almost the same as SPF, but Microsoft found a way to fk it up. There's info about Sender ID on the site above, and also on http://microsoft.com/senderid
Domainkeys is a little more complex to install, requiring modules or plugins to your mail server. A search should give you enough info to get started.
