The rank up and unlock system Call of Duty Black Ops 2 uses isn’t like we have seen before. As you rank up you unlock unlock tokens. You also unlock the ability to unlock weapons, perks and score streaks. The level cap is 55 (Commander). I’m not sure how many prestige levels there are, but traditionally the Call of Duty games come with 10 initially.
At the end of this guide there is a YouTube video with a visual version of this guide.
Each rank you go up, from rank 1 to 2 or rank 54 to 55, you get an unlock token you can spend on unlocking specific items. These include weapons, score streaks and perks. However, to even be able to spend a token on a weapon, score streak or perk you must be of sufficient rank to have the ability to spend unlock tokens on specific weapons, score streaks and perks.