Holy flu symptoms, Batman, give me an antibiotic...?

We've been seeing a lot of different illnesses these past few weeks, especially those of the runny nose, cough, sore throat, and achy variety. How do you know if you have a cold, the flu, or something else?
WebMD is a great source for lots of health questions (be sure to check out this slideshow on Cold vs Flu). Here's a table I copied from their website to help answer the question. You'll notice that antibiotics are NOT mentioned as a treatment.

Symptoms	Cold	Flu
Fever	Rare	Characteristic, high (100-102 degrees F); lasts three to four days
Headache	Rare	Prominent
General Aches, Pains	Slight	Usual; often severe
Fatigue, Weakness	Quite mild	Can last up to two to three weeks
Extreme Exhaustion	Never	Early and prominent
Stuffy Nose	Common	Sometimes
Sneezing	Usual	Sometimes
Sore Throat	Common	Sometimes
Chest Discomfort, Cough	Mild to moderate; hacking cough	Common; can become severe
Complications	Sinus congestion or earache	Bronchitis, pneumonia; can be life-threatening
Prevention	Good hygiene	Annual flu shot or FluMist
Treatment	Only temporary relief of symptoms	Antiviral drugs (Tamiflu or or Relenza) within 24-48 hours of onset