Your CMS should have a GUI (Graphical User Interface) that’s easy on the eyes, doesn’t have overly complicated options, and offers simplicity in its administration interface. A good interface means that tasks pertaining to creating and managing your content will be quicker, saving you a lot of time and increasing your productivity.

To get a better understanding of what the GUI looks like for each CMS look for video and tutorials on their websites and ask other people what they use and why?

What Themes, Plugins and APIs are available? and do they meet your current and future needs.

An API basically defines how a component interacts with a system, facilitating the communication between them. Plugin: also called an extension, a plugin is a software component that makes it possible to modify an existing computer program or platform, for instance, adding new features to it.

• URL management : A good CMS allows you to personalise URLs by including relevant keywords while avoiding URLs that are too long or complex.
• The structure of the site : A good CMS allows you to create a clear and logical tree structure to facilitate user navigation and indexing by search engines.
• HTML tags : titles, meta-descriptions, and header tags (Hn) should be filled in correctly to help search engines understand site content and prioritise it accordingly. Your CMS should allow easy management of these tags to make optimisations if necessary.
• The content : The CMS should offer easy content management and the possibility of regularly updating your site to keep it up to date and attractive for its visitors.
• Optimisation for mobile : The CMS must give the possibility of creating an adaptive or responsive website in order to promote an optimal user experience on all devices.
• The quality of the code: a clean code optimised for performance must be able to be generated, with a fast loading speed and a native reduction in the size of the files (images, CSS, HTML).

A good CMS should:

• enable SSL support.
  An SSL certificate is a digital certificate that authenticates a website's identity and enables an encrypted connection. SSL stands for Secure Sockets Layer, a security protocol that creates an encrypted link between a web server and a web browser. Companies and organisations need to add SSL certificates to their websites to secure online transactions and keep customer information private and secure.
• provide regular updates
• offer easy to use backup services

Make sure the CMS you choose has an active support community. The more popular the CMS chosen the bigger this community usually is.