How should I deal with lower back pain in gym training?

Squats and deadlifts are one of the best exercises for building strength and muscle. However just like any exercise or sport, there is always a risk of injury. And when it comes to these two exercises back injury is the most common. While doing squats you place the weight on your back, putting pressure on your spine. By squeezing your shoulder blades together, taking a deep breath while coming down (your lungs fill with air and protect your spine by separating the vertebrae), and only going down until your thighs are parallel to the ground, you will be reducing the risk of injury dramatically. I know that to get the full benefit of the squat you should be going down until your hips are below your knees, but that is when your hip will rotate forwards, putting all the pressure of the weight on the lower vertebrae and discs there, causing them sometimes to move or bulge and sometimes get inflamed. On the deadlift although no weight is directly impacting your spine, however the exercise itself focuses on the lower back, and the wrong movement or form will increase risk of injury as well. The rule of thumb is when you feel pain, STOP immediately, and the ideal situation would be to get your back checked with the appropriate doctor. I know it sucks and it is very tempting to just brush it off and continue your session or not stopping for a rest. Believe me I have been there and I regret it now since my lower back problem is now bigger, more permanent, and harder to get rid of. Take a few days rest, and check your self, do some lower back and glute stretches as Brett mentioned above, and then go back to your training when you don't feel pain anymore.  When you get back into it, start with lighter weights, ensure PERFECT form, and do everything slowly. Progress slowly and if you feel the pain again, my advice is to get your back checked as you might have injured it in way that needs medical attention. Don't worry though, no problem is without a solution. In the end if you feel or the doctor advises you not to squat anymore for example, there are many exercises that you can substitute the squat with, let me know if you need to know what they are. I have done that myself because of my back pain and I am progressing well on the exercises I am doing.