What is the most obvious way to tell other people you use Linux. Talk to them!
But what if there are too many people, and you can’t talk to [all of] them really… But still want to get the message “I am a Linux user” delivered? In this case, put this message on something visible. Computer sticker, mug, pen – the options are there. And, of course, with this summer season asking us to change clothes to something light, T-shirt is a nice way to promote your favourite operating system too!