Sadly, there's no sure-fire way to get over a cold faster. Your best bet is to stay in general good health, which keeps your immune system functioning at peak levels, and you'll get fewer colds and get over them faster. Too much vitamin C is unlikely to hurt, but most people in developed countries get enough from their normal diets anyway, so I wouldn't recommend a supplement. It's just a waste of money, for the most part.
Garlic also seems to have some strange, nearly magickal ability to bolster one's immune system, plus it's delicious. I can't find a flaw in the idea of artificially simulating a fever, but NyQuil and other medications that cover the symptoms are usually more likely to extend the duration of the cold by suppressing your body's natural immune functions. Cough suppressants are probably a horrible idea unless you're having a hard time sleeping because of your cough, but expectorants are probably good.