As the quads are a very big muscle group, including a thigh stretch in your workout is a great way to reduce the risk of soreness. All day long your quads are being worked as well, whether it is from getting up and down out of your chair, walking up stairs or bending to lift a box (using the correct lifting procedure and lifting from the legs), adding to the fact that they may become quite tight over time.
The solution to this would be a thigh stretch that helps to lengthen the front quad muscle. To perform it, bend one leg at the knee and grab a hold of the foot behind you. Slowly begin to pull the leg gently backwards while pushing your hips forward. This should create a feeling of tension running down the front of the leg. Hold this position for a good twenty to thirty seconds and then switch legs.
A second thigh stretch to perform is done in a similar fashion that you do a lunge but instead of remaining off the ground you actually place your knee on the ground for balance. Your hands can either remain on the knee that isn't on the floor or else on either side of you touching the floor. The lower part of the back leg should also be resting on the floor with the upper portion in a horizontal direction. Try and push your hips forward as much as you can to deepen the tension that you feel.
To start the last movement you can perform, get into a kneeling position on the ground. Your feet should be flat and bum pressed into the heels. Then slowly lean backwards until your back is now lying on the ground as well. Note that less flexible individuals will likely not be able to go all the way back and may need someone to help hold them as they lean back at first. Once your back is on the ground simply rest there for thirty seconds before coming up again. This one will predominately work the front quad as well as the hip flexor region.
So make sure you include one of these three movements the next time you are finishing up a workout.