1. Usage of y and w

• When there is no intials before finals starting with i, y shall be added as initial. If there is other vowels after i, i shall be changed to y. For example:
  ia - ya ie -ye iao -yao
  iou -you ian -yan iang -yang
  iong -yong    
• If no vowels after i, just y before i. For example:
  i - yi in -yin ing -ying
• When there is no intials before finals starting with u, w shall be added as initial. If there is other vowels after u, u shall be changed to w. For example:
  ua - wa uo -wo uai -wai
  uei - wei uan - wan uen - wen
  uang - wang ueng - weng  
• If no vowels after u, just w before u. For example:
  u - wu    
• When there is no intials before finals starting with ü, y shall be added as initial no matter if there is vowels after ü. When y added, ü is changed to u. For example:
  ü - yu üe - yue üan - yuan
  ün -yun    

2. Usage of ’ mark

When syllables starting with a, o, e follow other syllables and may make confusions, ’ mark is used to seperate them. For example:
piao 票                          jiang 讲                    minge 民革                          xian 先
pi ’ao 皮袄              ji ’ang 激昂             ming ’e 名额                   xi ’an 西安 

3. Abbraviations

• Abbraviations of iou, uei and uen
  When there is initials before iou, uei and uen, they are abbraviated as iu, ui and un. For Example:
  niou - niu guei - gui luen -lun
  If no initials proceed, then they still abide by the rules of usage of y and w shown above.
• When initials other than n and l proceed finals ü starting with, ü changes to u.
  nü - nü lü - lü jü - ju qü - qu
• When uo follows initials b, p, m, or f, u is dropped, resulting in bo, po, mo, or fo.
  buo - bo puo - po muo -mo fuo - fo
• The final er can follow other finals to form retroflection. In the follow case, er is abbraviated as r.
  When er is attached as suffix to finals a, o, e u, -ng. For example:
  bar 把儿 mor 沫儿 ger 歌儿 shur 数儿 rangr 瓤儿
  When er is attached as suffix to finals ai, an, en, drop the final letter and er is abbraviated as r. For example:
  hair 孩儿 bianr 边儿 pianr 片儿
  When er is attached as suffix to finals i and ü, er is shorted as r.
  pir 皮儿 qir 旗儿 qur 曲儿
  When er is attached as suffix to finals -i, in, and un, the final letter is dropped.
  sher 事儿