Normally, a "please stay on trail" sign is there to protect the environment from being trampled. In Hawaii, the tables are turned, and it's Mother Nature who kicks butt on hikers who wander. Sadly, people die monthly somewhere in Hawaii from a recreational mishap. Happily, almost all deaths and injuriess can be easily avoided. Here's a few tips:
1. Stay on trails. On mountain hikes, the greenery at the edge of a trail can hide a sheer drop off. Never head off in a direction based on a GPS reading. Venturing into the wilds is to get lost and tangled in flora, even when the terrain doesn't look like a jungle.
2. Don't let even big kids go jetting ahead. See above. And trail junctions are often not well signed. Keep the group together.
3. Don't cross a fast-moving stream. If you get caught on the wrong side, wait it out. People oftern get swept away. Streams rise on some occasions when rain is falling inland, unbeknownst to hikers.
4. A hiking pole is a very good idea. Ridge trails are often very steep and narrow. Going up is okay, but coming down can be difficult, especially when rain turns the hard-packed soils slick.
5. If you lose the trail, return to a known point. If the route is not passible, there is no trail fit for a human. Hawaii has been hiked for centuries. If it's possible to walk someplace, then a trail will exist.
6. Know how much daylight you have left. If you get caught out at night, stay put in most cases (good trail, flashlight is needed).
7. Carry an equipped day pack, even on short hikes. Lack of food, water, and outerwear can turn an inconvenience into a major eff-up, even a mile or two from the trailhead.