Everything has its place, and that includes static stretching. But, when we are talking about warming up and preparing for resistance training, static stretching isn't the best idea. Static stretching is when you lengthen a muscle to a point of resistance and hold that position for 30 seconds. Over that period of time, your nervous system realizes what is happening and allows your body to relax a bit and the muscle to lengthen and stretch out. So, what's wrong with that? Seems like a good and effective idea.
The problem is twofold. First, this lengthening of the muscle is temporary. Second, you haven't taught your body to recruit and use this newly learned flexibility. You actually have a greater chance of getting injured performing static stretching prior to lifting because you have created instability and weakness in certain areas of your muscles. Static stretching is best utilized after your workout when you are warm and the muscles can stretch further.
Dynamic warm-ups or mobility drills create the flexibility you seek while keeping opposing muscles tight and creating strength throughout non-stable areas. You will want to focus on the muscle groups you will be using during your workout. For example, if you are scheduled for deadlifts, perform dynamic warm-ups and mobility drills for your hips, lats/back, and hamstrings.
The final point to consider is your central nervous system (CNS). Recent science suggests that your CNS is responsible for flexibility and "turning on" muscle groups. It also gets the blood flowing and your adrenaline rushing. Try adding in some explosive movements that turn on your CNS before you lift and see how you feel!