My tiny black mantis hides almost all of the time with his little eyes sticking out from his den. He comes out when nobody is around and redecorates his tank. It took him about a month to start doing that though. Initially he just hid and would only eat every couple days. His absolute favorite are frozen enriched mysis shrimp and live dwarf cerith snails. If you order them from Reef Cleaners, they often send you about six trillion dwarf ceriths when you order 5 or 10, so I ask for extras for my mantis and that gives me about a 6 month supply. I keep the spares in my other tanks and toss a couple of them into his tank once a week. They don't last long.
His little tank is situated directly across from the TV, and every time we have the TV on, he's right there looking up at it, or looking over at us on the couch.
Just don't expect him to be super friendly until he learns to associate you with food... which he will.