I'm still quite new to badminton. Yesterday I had a coaching session. We did some work on my serve, and one thing I wanted to work on was to disguise my serve so you can't tell when I'm going to do the flick serve. When I showed the coach my serves I knew he'd notice a difference in the back swing, but before doing the flick serve he also noticed me tensing up and looking where I'm planning to hit it. I was wondering what might be some common tells in beginners apart from just the swing, or whether they typically give it away just by the swing.