It is boring. But if you're selling something in a group presentation or say for instance if you're training people in a group then doing subtle things like nodding your head to gain the commitment of those in front of you works. If you do it then you'll see people nodding back, providing your presentation/training is interesting and your product semi desirable.
When you're speaking to someone one to one, say a work colleague, when you're into the conversation then cross your arms and as long as you're not invading their space they'll eight times out of ten do similar. The same for when you're sat down having a talk with someone, practice leaning forward and back naturally and they'll often mimic it.