Should I stretch before I workout?

Answer: No.

Really. No.  You shouldn't stretch before you workout. 

Without getting into the science of it all (there is plenty of scholarly writing available on Google), think of your body as a car. 

Now this is a timely metaphor since it is less than 20 degrees outside and all of our cars are covered in ice.  Each morning before work, all of us take an extra 3-5 minutes to scrape the ice off the windshield and let the car warm up before heading out.  You wouldn't take the car on a stop-start trip, back and forth in the parking lot.  You might let it idle in park, or rev up the engine until the little heat meter moves a few centimeters up from "C".

Warming up your body serves the same purpose.  Another metaphor would be to stick a bandaid in the freezer for an hour.  Then pull it out and try to stretch it.  Odds are it probably won't be very flexible.  Scary to think your hamstrings and deltoids work the same way.  Take that same rubber band out of the freezer and stick it in hot water or in the microwave for a little bit.  Chances are it stretches much more easily. 

There are a number of ways to get warm (jogging, body weight squats, jumping rope, burpees, jumping jacks, mountain climbers, etc).  A "dynamic warmup" is basically a movement-specific way to get the blood circulating and the heart rate up prior to your key exercise. 

One of the biggest life-long values I received while running track in college was the art of the dynamic warm-up for both the legs and core/abs.  Here's a few videos demonstrating exercises that fall in the dynamic warm-up category:

Sprint Warm-Up:

GPP (General Physical Preparedness):