Call anybody you can reach to, even a family member is fine. Prepare on the screen the prototype, the mock-up, the demo of the visual artifact you’ve just created and you want to have feedback on.
Do not make any introduction, do not give any explanation: call the chosen tester and ask a direct and straightforward question: “What do you see?”.
As the first thing you want to have the first reaction, you want to listen to their thinking process. When they start to describe what they see, do not make any reaction, do not judge, do not answer. Keep on asking “and then?” or “why?” or “what does it make you think of?”. Ask only open questions to elaborate on what they are seeing and feeling.
Only when you are satisfied and their patience hold, if you feel like, ask them more specific questions like: “Do you like it?”, “What do you like?”, “What don’t you like?”.
And only at the end try to give context, application, and audience: “How do you see this ‘thing’ in the context of conveying this ‘message’ to these ‘people with the objective of achieving this ‘communication goal’”?
Congratulations, you had the chance of receiving brutally honest feedback.