Picture this. You call an employee into your office for a meeting. As your employee is explaining something to you, you turn to your computer monitor to check e-mail. Or, you answer your phone. Or, you look at your mobile device. Or, you engage in a conversation with someone who enters your doorway.
Do any of these once and your employee will likely forgive you. Do any of these actions regularly and you'll quickly lose the respect of your employee!
Rarely is there a reason not to give your employee your full, undivided attention during a meeting/conversation. You can only be a good listener if you are maintaining eye contact with your employee and not multi-tasking.