total used free shared buffers cached
Mem: 514432 505948 8484 0 8912 439112
-/+ buffers/cache: 57924 456508
Swap: 1044216 0 1044216

After doing the "free" command I get the above in my xterm. What is the correct way to read this to know exactly how much ram I have free? (I have googled, and it returned different answers to this question and I just wanted to post here to make sure I know the correct way to read it)

And as always, Thanks in advance.