E-infrastructures offer new possibilities of research but can be difficult to master by scientists unfamiliar with grid front-ends. Science Gateways (SGs) are emerging as promising tools, helping scientists engage with the e-infrastructure. Some are built for very specific tasks while others are shared openly by communities with common needs such as monitoring, workflow management or job execution. These tools are integrated through hidden layers so the interface with the user is based on a web portal, a desktop or even a mobile application. EGI-InSPIRE ran a Virtual Team dedicated to SGs with members from 15 National Grid Initiatives and collaborators from SCI-BUS/COMMIT. The goal was to produce a Primer, a manual focused on SG development. Key information was gathered from the EGI community, such as best practices on how to build SGs, and state of the art in relevant technology and policy areas. This presentation will provide an overview of this Primer and our key findings.