Nick, next time you get chicken that you believe should be okay but you just have doubts about - and I am not talking about having a smell of rotting corpses - look at the condition of the skin and the flesh first of all. Chicken that is going will be sticky to the touch of the skin and will look a bit dull. The meat can get a green tinge and the skin will have a yellow hue to it.
However, the chicken can smell when it is wrapped in plastic, especially if it is sitting in any blood. First of all, rinse the chicken thoroughly. If you still have any doubts about the chicken, chuck it. If there is a smell after it is rinsed, chuck it. If it all looks good and fine and you want to take the chance (baring in mind I said that you believe it should be good), don't cook it for other people to start with (!), but cook it for yourself, if it starts to smell - cease the cooking process and chuck it. If you think it is fine then, and you still want to have a try at eating it, do NOT serve it with any sauce or strong flavourings that may mask the condition of the chicken. And even then, if you have even the inkling of a doubt, chuck it out!!! Nine out of ten times (at least) you will still end up chucking it. Poultry food poisoning is nasty as has been said.
Too many restaurants, not enough time...