As hypnoctopus says. About the easiest way to promote activity is to provide more overall security. Especially for younger snakes. They're more apt to roam as long as they still feel "hidden" while doing it. Half logs, smaller hollowed logs, fake plants, vines, fake leaves, vines, vines (i can't stress enough how much they all seem to LOVE fake vines when they're babies), just about anything they can crawl though/in/under to avoid detection.
That being said, snakes very much have their own personalities. So some of them, you can try every trick in the book and they'll still just hide out all the time, even into adulthood. Most snakes aren't really pets you get to "watch" but pets you get to "interact with". Since most snakes are crepuscular bordering on nocturnal, the thought of just trying to watch them is moot.