I have been learning Chan meditation under Chan master YongHua at Lu Mountain Temple since 2012. Unlike most will think, meditation is not just to sit and relax. It actually requires a lot of hard work when you wish to practice it in depth.
Chan is a central practice of Mahayana Buddhism. Chan is a word originated from the Sanskrit word Dhyana. It means "concentration", "stillness contemplation" or "thought cultivation".
Now, you probably have a lot of rationalized thoughts and try to make sense of it. Meditation is all about "doing" it. If you do it, then you will understand. You will find countless books about why meditation is good for you, how it works, and all different theories of meditation, drop those thoughts and questions for now. Meditation is meant to be practiced and you will soon start getting answers from doing it. In Buddhism, it's called "unfolding inherent wisdom".
My teacher always emphasizes to sit in full lotus at least one hour a day. But for beginners, it sometimes takes many years to get there. Let's start 15 minutes daily with the following instruction. You will feel the difference in just few days. As your mind and body gets stronger, try to sit in full lotus and extend the length of time. You can overcome many physical and mental challenges naturally and find the balance to your life.
Chan Meditation Instruction
Body
Cross your legs in half or full lotus, if possible. For half-lotus, your left leg is on top. For full lotus, your left leg comes first, and right leg goes on top. You may also sit in the comfortable cross-legged posture or a chair. * If you can already do full lotus, go for it! If you can do only 1 minute of full lotus, it's still better than 15 minutes of half lotus.
Rest your hands palms upwards on your lap, right hand on top, with your thumbs touching.
Curl your tongue up to gently touch the gums behind your upper front teeth.
Keep your eyes closed or one-third open.
Sit with the small of your back straight.
Breath naturally, through your nose.
Do not move during meditation. Discomfort from crossing your legs is natural. Patiently endure as much as you can. Use a timer and sit two minutes longer every day. The pain will increase your concentration power, and also trigger a healing process in your body.
Mind
Silently recite the name of a Buddha, Bodhisattva, or your personal source of spiritual strength. For instance, we recommend reciting GuanYin Bodhisattva’s name (“GUAN YIN PU SA” in Chinese).
For beginners, I also recommend Breath Counting. It's simple and easy. Every time you breathe out, you count 1, 2, 3, ... up to 10. When you reach 10, you count from 10, 9, 8.. to 1 on every breath-out. Breathe normally but follow your breath to your navel (Dan Tian).
Drop all your thoughts and worries and place your attention at your navel.
If you are reciting, then forget about your breathing. Chan is simplification.
Alternatively, you may use your breath as the object of your meditation. In that case, instead of reciting, just place your attention at your navel and observe your breath; do not adjust your breathing in any way.
Extras
Wear comfortable clothing.
Sit facing a wall to reduce visual distractions.
Avoid drafts.
Keep your legs warm with a blanket or towel, if necessary.
Do not wear a hat if your head feels cold. Bear it until it naturally warms up.
Do not wrap a blanket around your upper body when it is cold. Instead, wear more layers; but it’s best to keep yourself slightly cool.
Most importantly, meditate consistently every day. One hour a day is ideal, but even 15 minutes a day will be very beneficial.