Hi there are a lot of books out there explaining body language and I would expect that your teacher has discussed some of them with you: eye contact, open posture/closed posture, arms crossed, swinging legs to name a few. Think about what you already know as this is something we do every day...we may not get it right all the time but we know what we are looking for when we meet someone for the first time. Do they smile at us, make eye contact, say hello, stand to face us or sit directly facing us, lean towards or away from us. We are reading someone's body language and respond accordingly. This isn't rocket science so relax and tap into your own knowledge source and trust your instinct. Good luck