Wah How to use Both of, Either of, Neither of.

We use Both of, Either of, Neither of to talk about which of two things or people does something.

1) Both means two of two things.
    I have two children. I love both of them.
    Both of us are having a good time.
    I don't know both of them.
    Are both of you ready to go?
    When I woke up this morning, both of my parents had gone to work.

We can use both after a subject or before a plural noun or object pronoun. 
    We both love the pizza.
    Both students passed the exam.  
    I couldn't decide between them - I liked them both.

2) Either means one or the other.
    Do you want tea or coffee? You can choose either of them.
    There are two pies. You can have either of them.
    You can take the bus or the train to get to town. You can take either of them.
    You may take either of the two books.

Wah How to use "So do I / Neither do I"

You can use So do I or Neither do I when you want to say something that is the same as others.

Positive sentence :  So + auxiliary verb + pronoun  :So do I, So am I, So have I...
Negative sentence : Neither + auxiliary verb + pronoun  : Neither do I, Neither am I, Neither have I...

For examples:

A: I am so excited.     
B: So am I.

A: I am not hungry.  
B: Neither am I.

A: John likes chocolate. 
B: So does Helen.  

A: Helen does not want to go out tonight.   
B: Neither dose John.

A: I have never been to Tokyo.
B: Neither have I. 

A: I can come the party tonight.
B: So can I.