Either/or, neither/nor

Punctuation

Use no comma when the parallel segments are in the same clause. However it is often acceptable to insert a comma before the second conjunction either to create a natural-sounding pause, or to prevent confusion.

It was either really stupid or really brave.

Use a comma when the two parallel phrases are in separate clauses:

Either you should come to visit us, or we should go to see you.

Subject-verb agreement

When subjects are joined by either/or or neither/nor, the verb agrees with the closer subject:

Either you or your friends are responsible for this

Neither John's friends nor John is interested in buying your car.

Word order

Independent clauses introduced by neither and nor both require inversion:

Neither does he understand the problem, nor does he care what happens.


Sources:
http://grammarist.com/grammar/conjunctions/
http://ericsquire.com/grammar/cnctors3.htm