What are the common body language signs to observe whether a person is interested in conversation or not?

Not: looking the other way, arms/legs crossed. Get a book on body language to learn more.

Some body language examples that might help.

rapt attention vs. fits of yawning.

Welcome to Fluther.

Well, on the “maybe interested” side you’ve got:
• waving money at you
• staring at you with eyes and mouth wide open
——
And on the “maybe not so much” there’s:
• sleeping
• spitting at your feet
• waving a gun in your general direction