The larger the files you can delete, the more space you can free. So let's go hunting. Click the Apple menu in the upper-left corner of the menu bar and choose About This Mac.
If this summary indicates that you are running Mac OS 10.12 Sierra or later, you can click the Storage tab to get a basic idea of what takes up as much space on your drive as documents , Photos, music and so on. For example, if you find that there is 100GB of music on a 128GB drive, you should clean up the iTunes library.
Click the Manage button to see a more detailed breakdown. The left sidebar displays each of the above categories, and you can click to see the largest files of that type. You may have several gigabytes of video from an old project that you no longer need or extensive iOS backups of devices that you no longer own.
Right-click on any of these files to delete them to be able to release a decent amount of space. (Do not forget to empty the Recycle Bin when you're done ̵
If you do not have macOS Sierra or want to get more detailed on your system You can use a tool like Disk Inventory X to perform similar tasks. While it's not the nicest storage analyzer available for macOS, it's free and offers a comprehensive list of folders, files and file types loading your hard drive.