The need to prepare your body for fast running is intuitive. What might not be so obvious is what makes a good warm-up. A jog of 1.5 to 3 miles is the first step, but not the only step. On the jog, start slower than you usually do on typical runs. This is really the day to gradually bring your body to life. By the end of your warm-up jog, you should be moving fluidly and faster than you were at the beginning without any real increase in effort.
Follow your warm-up jog with some dynamic stretches, like leg swings and skipping. Right before fast running, these are better than static stretching at preparing your muscles to work hard. Then do 4 to 8 striders of 80 to 100 meters, building into running faster on each one. Don’t worry that this fast running will detract from your workout; it will better prepare you to do the first couple repeats at the right intensity with the right range of motion.
If your workout is repeats of 2 minutes or more, after your last strider, run for 30 to 60 seconds at the pace you want to hit on the first repeat; on the track, running for 200 meters at that pace is convenient. This longer bout will prepare your internal plumbing systems to work at a high rate starting on the first repeat. Take a couple minutes of active rest (walking, more dynamic stretching) between this run and the first repeat of your workout.