How to fully utilize RAM to increase overall system performance

You should install Preload which will preload the software you use the most in your RAM (it'll learn which software to preload on its own). That's very easy to setup:

sudo apt-get install preload

You probably don't need to touch it, but if you want you can edit the options in /etc/preload.conf

You can add the following line to /etc/fstab to mount your /tmp directory into the RAM.

tmpfs   /tmp       tmpfs   defaults,noatime,nodiratime,mode=1777   0  0

This can be done with other directories, too. E.g. when you are compiling your code you can put the folder where the object files are placed and linked into RAM.

But pay attention. Data in folders that are mounted this way will be lost on any case of shutdown. Keep that in mind.

Besides from my knowledge there are many other helpful ressources available on this topic. For example this thread.