Normally, your schoold's ISO will file the petition for you. You and them talk about what documents are needed and to be signed. However, for your visa application you should have
1) Complete petition package (photocopy) your employer filed. The I129 is the form for H1B petition.
2) I797 (approval notice, need original).
3) Offer letter.
If you are a male, you also need to fill out DS157 form. It depends on where you go for visa application. They should let you know where to get the form.
Besides, if you have family members acompanying you then you need to have marriage certificate and birth certificate for children.