Often your prospective customer will ask if you would consider a discount, as a result this is a question that you should prepare for in advance. First, you want to discuss and agree on exactly what the rest of the terms will be and then you may decide to offer a discount to seal the deal. But be specific. Offering a discount in the range of 10-20% does not help move the deal towards a conclusion; it just makes you appear poorly prepared. Be confident and offer a specific discount (eg. 20%) that is within your affordable range.