Very rarely will children approach their parents and say, "Teach me how to study."  However, it would probably help a few parents if they did since many parents tell their children to study, but don't teach them how to study.  

Teach Me How to Study

There are not many skills one can learn in life as important as learning how to study.  Learning how one studies and learns best will allow a person to perform to the best of their ability in this very competitive world.  Life is full of tests and other instances when we must quickly learn information.  Effective study habits help people learn quicker and perform better on tests, which generally leads to more opportunities and greater achievements in life. 

Developing effective study habits requires one to experiment with different study techniques to see how one learns best, and then to rely on those same techniques each time one studies.  Eventually, those techniques become  habits, and the individual has developed a disciplined, effective way to learn.  Different techniques work for different people, so there is no one size fits all.  However, regardless of whether your child literally says the words "Teach me how to study" to you or not, take the initiative and help them try some of the below more commonly used techniques.

Effective Study Techniques

Determine which areas you are strongest in and which areas will require the most work.  Allocate more of your studying time to the areas where you are weakest and less time to sections you are comfortable with.

Take notes as you go through the material to highlight important concepts or problem areas.  Revisit these notes and highlights when you review.  See if you can explain important or difficult concepts to another person.  If you can’t explain the concept to another person you likely do not fully understand it.

Go through as many practice problems as possible in order to constantly gauge your understanding and retention.  When you get a problem wrong, read the solution.  If you still don’t understand the concept, then go back over the material until you do.  Practice problems will also give you an idea of the level of complexity tested on the exams, how long an average problem takes to solve, and the format of questions.  Your test taking and problem solving abilities will improve with practice. 
Try learning through different mediums.  Some people learn best by reading.  Others may learn better by listening, watching, or writing the materials down.  The more ways you are exposed to the material and the more senses you use the better.   

Use acronyms, mnemonic devices, or songs to help you memorize the material.  Memory aids can work wonders on an exam.

Remember that your brain will be sharper and you will be a better learner if you live a healthy lifestyle.  Exercise, get enough sleep, avoid caffeine, tobacco and alcohol, and eat healthy to make sure that you are at your best while studying.

Additional Learning Resources

Developing effective study habits is an important skill to learn in life.  Learning this at a young age has been a great blessing in my life as I have had to study and prepare for numerous exams.  Many students that do poorly in school are not dumb, they just haven’t figured out how they learn best and haven’t developed disciplined study habits.  Parents can be a great resource to their children in helping them realize what the underlying issue is and work to resolve it, without waiting for a literal request to "Teach me how to study" that will never come.

Fortunately there are a number of great books available on Amazon and in bookstores that discuss this in much greater depth than an article can.  You might take a look at Learning to Learn: Strengthening Study Skills and Brain Power, or one of the other great books available on the subject.