Great question!

I understand master points to be the point that can access the extra meridian point. IE: to access the Chong - needle SP4 - but I have not understood coupled points either. I will ask my acupuncturist tomorrow - who is an expert on extra meridians.

In the meantime - this is what I've found via surfing:
* Using the Points in Practice - Master & Couple Combinations:
* In general you needle the master point of the main meridian you are treating (due to symptomology) and then you needle its coupled point.
* For males it is common to needle the master point on the Left side and the coupled point on the Right.
* For women it is common to needle the master point on the Right side and the coupled point on the Left.

* Yin Qiao Mai Details
o Alternative names: yin heel vessel, yin motility vessel
o Master Point: KD 6
o Coupled Point: LU 7
o Xi Cleft Point: KD 8
o Intersection Points: KD 6, KD 8, UB 1
o Paired Meridian: Ren Mai
o Areas of effect: medial aspect of lower extremities, genitals, abdomen, eyes, throat, chest, lungs
nervous, muscular skeletal, digestive and respiratory systems
o Functions:
+ Controls the ascent of fluids and the descent of Qi
+ Movement of the body, walking, cold a/or weakness in the lower limbs
+ Digestive issues, abdominal issues
+ Urogenital problems, retention of urine
+ Respiratory issues
+ Excessive sleepiness
+ Eye issues
+ Hot Flashes
o Pathway: Originates at KD 2, travels upward to KD 6 and then to KD 8. It then continues up the medial aspect of the leg to the inguinal region where it enters the genitals. From the genitals it travels up the anterior abdomen and the chest to ST 12. From ST 12 it travels to ST 9 and along the cheek to UB 1 where it connects with the UB, GV and Yang Qiao Mai vessels. From there it rises upwards and enters the brain.

* Ren Mai Details - graphic
o Alternative names: conception vessel, directing vessel
o Master Point: LU 7

o Coupled Point: KD 6
o Luo Points: CV 15
o Intersection Points: ST 1, GV 28
o Paired Meridian: Yin Qiao Mai
o Areas of effect: face, thorax, abdomen, genitals, throat, chest, lungs
endocrine, urinary and digestive systems
o Functions:
+ "Sea of Yin:" influences the yin, essence and fluids
+ Regulates female cycles, menstruation (irregular, leukorrhea), reproduction
+ Effects male genitalia, hernia, sexual desire, impotence
+ Gastrointestinal issues, digestion
o Pathway: Originates at ming men and passes through the uterus and connects with CV 1. Then it follows the ren meridian up to CV 24. Along the path it connects internally with the SP, LV and KD meridians. At CV 24 a second branch rises upwards and encircles the mouth and then rises to the eyes at ST 1. A separate branche originates in the pelvic cavity and rises up along the back.

* Yang Qiao Mai Details
o Alternative names: yang heel vessel, yang motility vessel
o Master Point: UB 62
o Coupled Point: SI 3
o Xi Cleft Point: UB 59
o Intersection Points: UB 1, UB 59, UB 61, UB 62, GB 20, GB 29, SI 10, LI 15, LI 16, ST 1, ST 3, ST 4
o Paired Meridian: Du Mai
o Areas of effect: back, neck, eyes
nervous and muscular skeletal systems
o Functions:
+ Issues of the eyes a/or face, eye pain (esp. inner canthus), redness a/or swelling, headache
+ Effects the lateral aspect of the lower limbs, numbness, weakness, spasms
+ Excess Yang, insomnia
o Pathway: Originates at UB 62 and travels behind the heel to UB 61. It continues up the calf to UB 59, up the lateral aspect of the leg to GB 29 and then up to the scapular region at SI 10. It continues to LI 15 and LI 16 and then travels to the face and connects with ST 4, ST 3, ST 1 and UB 1 where it meets with the UB, GV and Yin Qiao meridians. From here it travels over the head and terminates at GB 20.

* Du Mai Details - graphic
o Alternative names: governing vessel
o Master Point: SI 3
o Coupled Point: UB 62
o Luo Point: GV 1
o Intersection Points: CV 1, UB 12
o Paired Meridian: Yang Qiao Mai
o Areas of effect: Posterior midline especially spinal cord and brain
nervous and muscular systems
o Functions:
+ "Sea of Yang:" effects all of the yang meridians
+ Brain, marrow a/or spinal cord issues - pain, heaviness, stroke, psychological issues, etc.
+ Other facial issues - headache, migaraine, pain/swelling in the face/head
o Pathway: Originates at ming men and descends to the perineum, emerging at CV 1/GV 1. Then it continues to GV 4 where it enters the kidneys. From the kidneys it travels up the interior of the spinal column to GV 12 where it goes laterally to UB 12 and then back to GV 13. From here it continues along the midline of the head to GV 16 where it enters the brain and ends at the frenulum of the upper lib (GV 28).

* Yin Wei Mai Details
o Alternative names: yin linking vessel
o Master Point: PC 6
o Coupled Point: SP 4
o Xi Cleft Point: KD 9
o Intersection Points: KD 9, LV 14, SP 13, SP 15, SP 16, CV 22, CV 23
o Paired Meridian: Chong Mai
o Areas of effect: Medial aspect of the lower limbs
nervous, cardiovascular, muscular skeletal and digestive systems
o Functions:
+ Effects the balance of Yin and Yang
+ Effects the Blood, Yin and Shen - blood circulation, heart pain, depression, blood deficiency headaches
+ Pain in the chest, back, middle and/or lower jiaos - abdominal distention, ST ache, nausea, rectal prolapse
o Pathway: Originates at KD 9 and goes up along the medial aspect of the thigh into the abdomen where it enters the spleen meridian at SP 13, SP 15, SP 16. It continues up to LV 14, enters the abdomen and continues upwards through the chest and throat. It then meets the ren mai at CV 22 and CV 23.

* Chong Mai Details
o Alternative names: penetrating vessel
o Master Point: SP 4
o Coupled Point: PC 6
o Xi Cleft Point: GB 35
o Intersection Points: KD 11 thru KD 21, CV 1
o Paired Meridian: Yin Wei Mai
o Areas of effect: Abdomen, thorax, genitals, Heart, inner thigh
reproductive, digestive and respiratory systems
o Functions:
+ "Sea of Blood:" menstrual a/or reproductive issues, irregular menstruation, infertility
+ Physical and spiritual heart issues - Heart pain, depression
+ Balances rebellious Qi - hiccups
+ Abdominal stagnation
+ Respiratory issues - SOB, asthma
o Pathway: Originates in the ming men and passes through the uterus and down to CV 1. From here it emerges at ST 30 and continues upwards along the kidney meridian to KD 21. It then flows up the throat, encircles the mouth and continues up to the forehead.
A second branch flows from CV 1 inside the spine to the UB 23 area.
A third branch flows downwards towards the foot where it splits into 2 branches and follows the KD and SP meridians.

* Yang Wei Mai Details
o Alternative names: yang linking vessel
o Master Point: TH 5
o Coupled Point: GB 41
o Xi Cleft Point: GB 35
o Intersection Points: UB 63, SI 10, GV 15, GV 16, GB 13 thru GB 21, GB 35, TH 15
o Paired Meridian: Dai Mai
o Areas of effect: Sides of the body, hips, joints, eyes, ears
muscular skeletal and immune systems
o Functions:
+ Shao Yang level illnesses - alternating fever and chills
+ Pain a/or distention in the lumbar region
o Pathway: Originates at UB 63 and ascends along the the GB meridian up the leg and sides of the body passing thru GB 35. It continues to UB 59 and up to the hip (GB 29). Then it continues along the lateral aspect of the body to LI 14 at the shoulder, to TH 13, TH 15 and to GB 21. It then travels down to SI 10, over to GV 15, GV 16 and then to GB 20. It continues downward along the GB meridian from GB 19 thru to GB 13 where it ends.

* Dai Mai Details
o Alternative names: belt vessel, girdle vessel
o Master Point: GB 41
o Coupled Point: TH 5
o Intersection Points: GB 26, GB 27, GB 28, LV 13
o Paired Meridian: Yang Wei Mai
o Areas of effect: lateral sides of the lumbar area
gastrointestinal, female reproductive and muscular skeletal systems
o Functions:
+ Issues in the middle aspect of the body - abdominal distention, lumbar weakness, muscular weakness in the lumbar a/or lower extremities
+ Links the upper and lower halves of the body and helps to move Qi and Blood in the legs - weakness in the legs, walking problems
o Pathway: Originates at LV 13, continues to and encircles GB 26 and LV 13 and then connects with GB 27 and GB 28.