Besides what Lufbrarunner mentioned above, I use the application Memory Clean 2 whenever I want to clean up memory:
Memory Clean is the ultimate app for optimizing your Mac's memory and is best used after you have finished using a memory (RAM) intensive app or game.
fiplab.com
Both of my Macs have 8 gig of Ram, and about 99% of the time, I run only one application. When I need to use Memory Clean the most is when, via my browser (Brave), I visit yahoo.com. It seems that no matter how many of the stories there I click to view on, my available memory drops to less than 4 gig. When I leave yahoo.com (typically to check gmail.com for mail), I'll click on the Memory Clean 2 icon to clean up my Ram. It typically takes 2 or 3 such runs to do it, and I get back to 5.5 gig of Ram.
Some people do not believe in using such a program, but it works for me. There are some applications (and web sites) that do not "give back" the memory they used when one quits the application (or leaves the web site). I've heard comments in the past that the Mac OS "manages" such memory usage, but I have yet to see it.
Some other considerations:
1. How much free space do you have on your internal device?
2. Do you have any applications launching at start up? (I have none).