Introduction to Chinese alphabet (Pinyin)

Basic Chinese Pinyin Rules
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:

If no vowels after i, just y before i. For example:

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:

If no vowels after u, just w before u. For example:

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:

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: 

3. Abbreviations
Abbreviations of iou, uei and uen
When there is initials before iou, uei and uen, they are abbraviated as iu, ui and un. For Example:

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. 

 When uo follows initials b, p, m, or f, u is dropped, resulting in bo, po, mo, or 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:  

 When er is attached as suffix to finals ai, an, en, drop the final letter and er is abbraviated as r. For example:

When er is attached as suffix to finals i and ü, er is shorted as r.

When er is attached as suffix to finals -i, in, and un, the final letter is dropped.