Final answer:
An efficient tip for using IM in business is to use it when an immediate response is needed, but not for confidential or lengthy messages.
Step-by-step explanation:
When considering IM for business communication, it is important to use it efficiently and effectively. Professional communication and etiquette dictate that IM should not be used for sending confidential information or lengthy, complex messages due to the casual and instantaneous nature of the medium.
Moreover, IM is not ideal for personal messages in a professional setting, as it blurs the lines between work and personal life, which should be kept separate to maintain professionalism.
One should avoid using IM unless a rapid response is necessary. It's more appropriate for brief, direct communications that require quick attention.
Keeping yourself available for IM during office hours can be helpful, but should not impede productivity. Therefore, the most effective tip among the options provided would be to use IM when in need of an immediate answer.