[Part of the NegotiatingPatternLanguage]
Any party in a negotiation will have an advantage if the negotiations are conducted on their own turf--this is why many car salesman, for instance, are reluctant to negotiate anywhere but in the dealership's offices (and are often unwilling to quote any price below sticker price over the phone). If negotiations are conducted on your own turf, you have the following advantages:
Greater access to information. The other party may be cut off from the world; and have to rely on memory and whatever notes they bring.
Ability to control the environment. Lighting, temperature, and other things can be used to influence a customer.
Ability to stall. If the negotiations drag on, you can get productive work done while the manager considers an offer (stalling is a frequent tactic; see also AbsentProxy). The other side, on "foreign" turf, likely will get bored and frustrated.