I use an AlienWare Quad-core i7 laptop with 16GB of RAM and an SSD. Even with this much hardware on my side my memory utilization may go near 100%. I am usually running numerous apps at the same time (code editors, photo editors, databases, web hosts, programming tools, etc.).
The strange thing is that if I start closing down apps, the memory utilization may not go down as much as I would expect. It seems that some of the programs I use do not always release the memory they allocated properly so even though I shut down the app, the memory it allocated still shows as tied up and is unavailable for my remaining running programs.
Then I discovered RAMMAP!
This is a tool by Sysinternals that will help you to release the allocated memory that these programs did not release. To use it, simply download it and run it (it is a single EXE that does not require an install).
Select:
Menu -> Empty -> Empty Working Sets
As soon as you select this option, you will see a dramatic drop on the amount of utilized memory in your computer.
Best of all this tool it FREE! If you want a copy of RAMMAP go to:
http://technet.microsoft.com/en-us/sysinternals/ff700229.aspx