Open Activity Monitor
Click the Memory tab
Check Memory Pressure
Review Memory Used
Review App Memory
Review Wired Memory
Review Compressed Memory
Review Cached Files
Use the Memory column to sort apps by usage
Open Finder
Click Applications
Open Utilities
Open Activity Monitor
Use Spotlight Search and type Activity Monitor
Click the Apple menu
Select About This Mac
Click More Info
Open System Report
Check Memory under Hardware
Use Terminal and run vm_stat
Use Terminal and run top
Use Terminal and run memory_pressure