Drupal 7: how to build a form system I want to build something like:
We have 2 type of users: staff and student.
Student logins into a drupal site, then a collection of forms presented to the student
Form type 1: Student selects a form then fill in all fields. After hitting the submit button, data will be saved as a node.
Form type 2: Similar as form type 1, except the same student visits the same form, s/he will see the previous data s/he entered.
Very similar situation for staff.
I wonder what are the basic steps I need to take.
I can't give the complete solution, Yet I will try to relate things what you have asked to things what we have in Drupal,


Form type 1 =>  Any Node type (say Article)
Form type 2 =>  Any Node type (say blog)
Student => Drupal User (has a profile of student, use profiles2 module )
Teacher => Drupal User (has a profile of Teacher, use profiles2 module )


User Permissions for Node creation, Node edit by its own author. Views to display the forms and user redirection module to get something you want.