Personally for me stretching is very important. Especially after a workout stretches help to loosen up the muscle and can help the body regenerate faster. Weight lifting can put a lot of pressure on your muscles and your body. To reduce this pressure stretching is a good exercise. It can also be done infront of the TV in the evening. So why not just do it, right?
Static stretches before the workout are not recommended, since if they are performed on cold muscles, the chances that the muscles rip and tear are higher. Dynamic stretches though are recommended, since these warm the muscles slowly, so they prepare them for a more intense workout. Dynamic streches include rotating of the shoulders and arms (windmills), sun salutation, leg swings, fire hydrant circles or bodyweight lunges.
I always, always always do windmills before working out. They are perfect to warm up shoulders and arms. And warm shoulders and arms are important for every workout, even if you are not targeting this specific muscle group. Even for barbell rows, flies or deadlifts. You are always going to use a little bit of arms and shoulders, so a couple minutes windmills in each direction before every workout prepare your shoulders and arms.
I do have to admit that I am not always following this suggestion and I sometimes build static streches into my pre-workout warmup. If you do so as well, please be carefull and ease into those stretches, as you don’t want to force cold muscles in a streching position. Go very slow and stop when your body tells you to. When you want to go heavy I wouldn’t recommend static stretches at all before the training. You can do them afterwards as a cool down.