First, you need to have 2 more years related experience on whatever you offer says you are going to be engaged to.
you have a relevant degree on the field you are going to work on. The higher the better. The degree need to be notarized.
Second, In your offer letter, your company has to clearly states what is your job description, responsibility etc. Never says you are going to write code for them!
Those 2 pieces are the base documents you need to supply.
When you meet with the border officer, try to convince him that the offer is a temporary based and you never have any intention to immigrate to States.