First and foremost, you have to understand that corporate end users usually don’t get back to you as quickly as other end user types. A lot of times, they will reply in a painfully slow manner. This is because in a lot of cases, the party you are interacting with needs the approval of other people before making a decision. He cannot just decide how much to counter with or whether or not he should accept your offer. He might have to contact another department or one of the higher ups, I’m sure you get the point. As frustrating as it may be, you have to understand that that is simply how things stand and resist the temptation of sending countless follow-up emails because it tends to weaken your negotiation position.