Basic spam prevention
Sender Policy Framework (SPF) seeks to fix some of the historical issues with email. It does this by helping an email recipient (or mail server) determine whether the email has been sent from an authorised source (usually a hostname or IP address).
Once implemented, this makes it harder for a spammer / scammer or attacker to spoof or forge email from your domain.
SPF is implemented through a special record in your domains DNS (Domain Name Services). Mimecast (a fine security vendor) have created a number of tools to help people implement this as well as some helpful guidance.
Email reputation and content protection
Due to the fact that email is often relayed and is usually in plain text, another issue with email is that it can be intercepted and modified in transit.
Domain Keys Identified Mail (DKIM) builds upon SPF (above) and adds some cryptographic protection to address this. This helps to validate that email has not been tampered with and is authentic. Mimecast have also provided some good guidance on DKIM implementation.
Domain-based Message Authentication Reporting and Conformance
Once you have both SPF and DKIM implemented as above you can look to implement the next layer of protection. Domain-based Message Authentication Reporting and Conformance (DMARC) provides a reporting mechanism that helps to prove authenticity of email from your domain as well as reporting on attempted abuse.
Details on DMARC and its implementation can be found here. In addition, the website provides very useful checking and validation tools.