Communication to me is made up of several things. It starts with a clear idea in my head or setting my intention. Then I think carefully about my body language, verbal cues or tools I will use and the clear precise way I will use them. Another important piece is giving you and your horse time to read and respond to each other. And how much energy you are going to need. So if I make a request, I need to make sure I am clear and wait to see what my horses response will be. If he responds well, I can positively reinforce the response with praise, a release, or food, If I don't get any response, or the horse offers something other then what I requested, I can decide how I want to proceed after that. I may also make the task easier or simpler if I feel that is the problem.
A problem I often see is people moving too quickly with their cues and body language without thinking and bombarding their horse with too many signals. One of two things happens then, The horse is confused and doesn't know what to respond to first or they get desensitized to the language seeing it as "noise" or chatter.
It is important to break exercises into very small parts and build on and positively reinforce the smallest positive effort. You will engage your horse and create a willing participant who will seek out the next task with enthusiasm and interest.
Ask yourself if you have taken the time to be clear yourself before you make a request to your horse and get frustrated with his response. Also, take time before you ask for each thing and ask for them one at a time increasing the difficulty as your horse gains confidence and going back to an easier exercise if need be. Ignore any "wrong" answers as long as they are not dangerous, rude or disrespectful. Focus only on the positive reactions your horse gives. You will see you sessions together get better and better.