Ram is like food. If you don't have enough then it causes problems, but if you have too much, then a bunch of it simply goes unused.
If you are doing web browsing and video games, then 4GB is sometimes not quite enough, and 8GB is plenty (at least for the next few years). If you are doing a lot of multi-tasking, or light to moderate content production then 8GB may not quite be enough, but 16GB is generally plenty. If you are doing a lot of production work every day then 32GB is generally going to be plenty, but 64-512GB of ram is not unheard of.
So how much do you need? Open up your web browser with a bunch of websites. Open up a few office documents, a media player, and a few utilities. If you are doing editing then open up Premiere, or Audition, or whatever you use, and import a bunch of random content into the project. Then open up a large video game like Skyrim. This will bring a sort of worst case scenario of how much Ram you need.
Next, open up Task Manager and under "system" look for the line that says "Commit (MB) xxxx/xxxx" The first number is the amount of Ram addressed with some sort of information, and the 2nd number (the divisor) is the total amount of memory available to your system. This includes your system Ram and your virtual memory (using your HDD as Ram). If you are using 45% or more of that 2nd number (90% of your system Ram) then you need more Ram. If not, then there is no benefit to having more memory.