What to do for a back ache?

A few home remedies are:
- An oil prepared from garlic and rubbed on the back will give great relief.
- The juice of one lemon should be mixed with common salt and taken by the patient twice daily. It will give relief.
- Vitamin C intake of about 2000 mg daily also shows effective results.
The diet of those suffering from backache should consist of a salad of raw vegetables such as tomato, carrot, cabbage, cucumber, radish, lettuce, and, at least two steamed or lightly cooked vegetables such as cauliflower, cabbage, carrot, spinach, and plenty of fruits, except bananas. Some of the Yogic asanas are also useful like bhujangasana, shalabhasana, halasana, uttanpadasana and shavasana, along with some stretching exercises.

Hey Stuti....
Back pain can be because of various causes. So depending on your causes, the treatment would also differ. Normal ergonomic awareness, back stretching and strengthening exercises for your back would work better for any normal back pain. Some points Neha have already discussed.
Some other i would like to add are:
#Never sit continuously for more than 2-3 hours, go for a small round and do some stretching exercises.
#Never lift any heavy weights keeping at a far distance from your body. Keep it close and maintain your back in upright position.
#Do Back exercises like shalabhasana, rowing, etc.