I'm new to console gaming (XBOX) and I have 2 simple questions for you.
1- When buying used games that have an important multiplayer/online component, can you still play with your own profile?
i.e. COD or Halo game being played by someone who bought a "used" copy.
2- Some games (I'm thinking of Assassins Creed) have XBOX Live points that are awared when accomplishing game achievements. How does that work with "used" copies? Surely, these points can only be rewarded once to an account, right?
1. The profile you have on your Xbox is used for playing online and are not tied to the game in anyway. You do miss out on any included bonuses though.
2. Achievement points have no monetary value. You get points for achievements but you really can't do anything with them. Think Trophies for PS3. If there are any bonus items that have a redeem code then you more than likely will not get those with a used copy.
You might want to check on specific titles. I know EA for example has at least mentioned that they would consider requiring activation of sorts which ties a games online features to a specific profile. Therefore if you were to buy such a game used you would have to purchase an additional activation for your profile in order to use online features. I'm not sure if this has actually been implemented in any games yet though. Your best bet is to ask the store employees wherever you buy used games.