There are several different categories of interpreting. The type of interpreter you require will be determined by the situation in which the interpreter will be working.
Broadly speaking, interpreting falls into 2 types:
Consecutive, where the interpreter will relay what has been said while the speaker pauses
Simultaneous, where the content is conveyed in real time by the interpreter while the speaker is speaking
This is a kind of consecutive interpreting sometimes used in large and unstructured meetings. Typically, the participants will be able to communicate to a certain level in one or other language and the interpreter is required to be on-hand to help out when communication becomes difficult.
The most popular kind of interpreting. This is a type of consecutive interpreting where the interpreter waits until the speaker pauses at an an appropriate juncture before relaying the content into the target language. Typically used in business meetings, factory visits, presentations, speeches and other situations where there is direct interaction between the Japanese and English-speaking participants. You should schedule longer than usual for such meetings to allow time for the interpreter to translate.
This is a form of simultaneous interpreting typically used in large meetings where the content is directed at a number of other people besides those listening to the interpreter. An example would be a large meeting in a multinational company where the majority of the participants are able to speak and understand English but one or a few visitors from Japan do not, and require an interpreter. The interpreter sits close to the person (or people) for whom he is translating and whispers simultaneous translation so that the participant(s) can follow the meeting without its flow being disrupted by breaks for the interpretation.
Conference interpreting requires interpreting booths, microphones and other specialist equipment for the translation to be relayed to those listening through headsets in the auditorium. The work is demanding, and interpreters usually work in pairs, alternating throughout the day.
Interpreters do not normally require specialist equipment, except in the case of conference interpreting (see below).
Interpreters do require as much background information as possible before undertaking an assignment. A good interpreter will research the assignment before beginning.