I warm up before every session I do and my warm-up routine is similar for most my sessions whether they be weight training, sprinting/plyometrics or aerobic conditioning.

I start off with foam rolling (self massage tool) for the major muscle groups involved in that particular session.

I then do some light static stretching of certain muscle groups that have a tendency to be tight for me (hip flexors, calves, groin, hip rotators, hamstrings).

After that I move on to dynamic mobility drills for the thoracic, hips and ankle complex, as well as activation exercises for the scapular stabilizers and gluteals.

For sprint training I will do some additional running specific warm-up drills such as A's, B's and short sprint build-ups.

Most of the warm-up mobility exercises I use are covered in Parisi Warm Up DVDEncyclopedia Of Joint Mobility DVD and Magnificent Mobility DVD, which are all very good resources for both improving mobility, posture and physical preparation for athletic performance.