What's the best way to make unwanted guests leave?

At some points in life some guests may not be useful at the moment this makes not to want to have them around us. Below are some nice ways to make them leave without hurting them.
You and whoever was discussin can decide to change the topic to one which is so boring and not making any room were the unwanted guest can come in.
Also excusing yourself to the bathroom for Avery long time.
We can still apply the method of pretending to have something doing.