How to make sequence diagram for sign up

Question

I'm preparing the sequence diagram for a project. I started with the sign up operation.

It's confusing to me because this is the first time I use this technique with a real project.

The following image is part of the registration process, would any one take a look and correct me if I did any mistake.

http://i.stack.imgur.com/Of3qA.jpg

Answer 1

This looks good. I would suggest avoiding use of alt and doing only one scenario per sequence diagram. Label the sequence diagram with a note containing summary, precondition (what has run before), and postcondition (the state after the scenario has run).