Unfortunately not all injuries can be avoided. Once you get an injury it is important that you know how to treat it. There are many different types of injuries and I will list some of the more common ones here. For bad injuries it is important to seek professional help. Do not take advice in an article over a doctor's advice. This should be used as a reference and nothing more.
Different Kinds Of Injuries
Cramps Or Muscle Spasms
A spasm is just a contraction of a muscle. This is a defense used by the body to prevent further use of the muscle until is has recovered properly. Rest is the only thing needed to get past a cramp.
For general pains it is a good idea to quit the activity that caused the pain. You should rest until there is no longer any pain in the area. Do not become impatient and try to work around an injury. This could cause further damage and even more wasted time from the gym. Rest is the key to recovery.
This occurs when the ends of bones are no longer in the proper relationship to one another. Relocation may occur spontaneously if there is only a partial dislocation. If the force was great enough a complete dislocation could occur in which case medical attention will be necessary, as relocation is unlikely to occur by itself.
Specific Body Part Injuries
Calves have a tendency to pull and tear when they are subject to heavy exercises or occasional overtraining. The best way to avoid this injury is to stretch and warm up the calf with light sets before exposing them to higher weight. In minor cases just stopping exercising the calf is fine until the tear heals. If there is swelling try using ice. For serious injuries it is recommended you consult a doctor.
Learn more about the anatomy of the calves,
The knees endure heavy stress, especially while doing exercises like squats. Injuries can range from pulls to tendons attached to the knee or the injury could be located in the knee itself. Sprains could result from any twisting motion in the knee especially while doing the full range of motion doing a squat. Care should always be used when doing heavy exercises on perfect form. Knees should be warmed up properly before being put under heavy stress as a tear in the knee could require surgery. Wraps may also be used to help support your knees if necessary.
When a strain occurs the pain may be felt in the knee. In reality it is actually the leg muscle that is the problem. Another place that frequently gets injured is the hamstring; this is almost always due to inadequate stretching.
Tears can occur in the abdomen as well as any other area. Abdomen tears (or hernias) are more common among men because they tend to perform heavier lefts, which could directly cause the tearing (deadlifts for example). Hernias are caused by tears in your abdomen, which allow viscera to move through. Not holding your breath during lifts is important because it stops the building of pressure before it gets to a dangerous level. Hernias often require surgery as a treatment.
Learn more about the anatomy of the abs,
Spinal erectors are in danger of being over-worked when doing movements such as leg raises and deadlifts. Leg raises are a problem when the lower back leaves the safety of the bench where it can become hyperextended. You can strain your back or you can rupture a disc in your back. Inside of your vertebrate is a material needed by the vertebrate. Once you rupture the disc that material escapes and presses on surrounding nerves, this is why you experience pain. Depending on the nerve that gets pressed on the pain can be immobilizing.
Learn more about the anatomy of the back,
Pressing movements put a lot of stress on the elbows. Bad technique and heavy lifting can cause problems that can be very difficult to detect since the pain could be minor at first. If untreated the damage could be irreversible. A good practice is to wrap the elbow (and knees for that matter) during very heavy lifts.
The arms are a very complex body part, which includes many areas, which could succumb to injuries. The arms are also often over trained heavily by many people. People tend to over train the arms thinking they will build larger arms that way when in fact it is a great way to beat down your arms making them a prime target for injuries. Bicep pulls are rather common for people who like to curl heavy without warming up first.
Pulls can usually be felt close to the elbow. Once the bicep is pulled it is important to let the muscle rest. Only when the muscle is fully healed should it be trained again. I am speaking from experience here. I have pulled my bicep many times and have attempted to train it again much to quickly. All that did for me was aggravate the injury more, keeping me from training the muscle properly for extended periods of time.
Learn more about the anatomy of the arms,
Forearms are put under a lot of pressure when the biceps are trained due to them being a supporting muscle to the biceps. This also means that they are being worked when you work out your back. This is because the forearms are used any time you squeeze your hand together. Forearms should be warmed up lightly before heavy lifting. But more importantly than that is to make sure you do not lift to heavy when you are isolating your forearms. Make sure your reps are not to low, as a pull in the forearm can keep you from training many parts of the body as your need your forearms to grip the weight.