Well ideally you want to have the least amount of processes running and basically you would look for processes that are taking up too much memory and end them, depending on what it is.. Your physical memory should be under 14%.. Fraps, origin, firefox all that stuffs gotta go when u wna play crysis...
Well i dont think overclocking your cpu will make a huge difference to be honest unless the game is particularly cpu bound which i doubt as the other crysis's never really had abnormally high cpu usage.. Despite this, if you really want to overclock your cpu you need to download Intel Extreme Tuning Utility (IETU). Although you should be careful with this utility as some people have had issues where their system crashed and the overclock became default in the bios setting n screwed them over BIGTIME. Never happened to me ive used it alot but jus thought you should know its a bit dodgy..
Anyways about OCing, your system is already able to hit 3.3ghz because it is set to automatically oc itself called 'Intel Turbo Boost' up to 3.2/3.3 from 2.3ghz.. With using IETU to OC your cpu, it will allow you to change your main reference clock that affects your maximum turbo boost figure and also your minimum Ghz which is 2.3 stock. The highest you can OC absolutley safely is about 105Mhz on reference clock which essentially makes your cpu frequency 2.4 - 3.46Ghz from stock clocks which is 2.3 - 3.3Ghz.
heres an example -
Ive tried this and it gave me like +10-15 fps in planetside 2 which is an MMOFPS and becuase of thousands of players it relies heavily on the CPU.
For Crysis i personally think you would benefit from OC'ing your GPU to about 750/1650.