I hope you have heard this before, but the basis of any friendly negotiation is knowledge, not power. You aren't going to compell your future boss to raise his offer by threatening her, but you might be able to convince her that the offer is, as we say, 'below market'. That means you have to know what people in the same industry with the same skills in the same role are being paid. There are various sources for this information and your college counseling office should have access to the various references. But make sure you looking at the right comparables and don't inflate your experience and value. Have a rough idea of what the pay scale is for the position you are applying for before an offer is made.