Preparing your muscles for your workout is just as important as your workout alone!  jumping straight into your workout without the proper warm up can only get you into trouble!
What muscles you are you going to be working during that workout session?  From there, organize how you will prepare and warm up those muscles and surrounding muscles.  For example, if you are working upper chest/front delts, you need to stretch chest, triceps and shoulders.  For many of us who do full body workouts, we need to stretch everything!  For example,

You only need to do one set of each stretch, but make sure to hold it for 30 seconds before moving on.
Quads — Get into a lunge position with your knee on the floor and hold on to your rear foot. Be sure to stay tall, and if possible, reach for the ceiling with the same arm as the leg being stretched.
Hamstrings — While standing, put your heel on a bench. Make sure your knee is as straight as possible. Hold your pelvis with your hands and stand tall. Now simply tilt your pelvis forward until you feel a deep tweak along the hamstrings belly. It won’t take much. Avoid rounding your spine.  Another favorite is stand on one food and bring outside of the foot that is not touching the floor to the top of your quad.  Sit back like you are sitting in a chair and feel the stretch in your hamstrings and glutes!
Chest — Face a wall, and place one palm (reaching with a straight arm) against the wall at eye level or slightly above. Begin slowly moving the entire body away from the wall, while maintaining full contact with your palm. When you feel a good stretch through the chest, deepen the stretch by a) depressing your shoulder and b) rotating your elbow towards the floor.  Another favorite is to grab your hands behind your back and open up your chest as much as possible!
Lats — Hold any support beam either with palms facing the beam or away from the beam.    Bend forward with a flat back while holding the beam and “fall away” from it. Let your weight fall into your seat, so your body is only being held by the hand holding the beam.
Upper Traps — Hold a light dumbbell in your left hand. Let it hang straight down by your side as you take your other hand and place it on the rear left side of your head. Gently pull your head downward and to the right.  Repeat on the other side.
Glutes — Sit on the floor as though you were about to sit cross-legged, but put one leg straight back. Lean with a straight back over your knee.
I know how monotonous stretching may seem but it is just as imporant as your workout!! If you are looking for optimal results, be sure to stretch and don’t miss out on this essential puzzle piece!  You need every piece of the puzzle to achieve your optimal goals and to avoid injuries!
Remember, a solid training program isn’t just a bunch of exercises thrown together with random sets and reps. You need to prepare your muscles with a warm up before and during your exercises to prevent injury, activate muscle fibers,decrease tightness, and to get the most out of your workouts!