Adding trail running to your training routine is a great idea. Not only is it a great way to enjoy your local natural offerings, but it also works different muscles than road running, is less stressful on your joints, can improve your ability to focus, and is great for stress reduction.
However, you can't just wear any pair of running shoes when out on the trail. There are some specific features you should look for when purchasing a pair of trail running shoes. And, to be even more specific, the shoes you purchase should be made for the type of trail on which you plan to run. In addition to the characteristics you would consider for a pair of road shoes, such as size, cushioning, and drop, you will also need to consider the grip or traction and foot protection.
Trail shoes are broken down into three basic categories: light trail; rugged trail; and off trail. Light trail shoes are the most similar to road shoes and are made for groomed trails and gravel paths. They are usually the most lightweight of trail running shoes, offer average protective elements, are moderate in stiffness, have shallow lugs, and can vary in midsole cushioning based on your personal preference.
Rugged trail shoes are for running on hiking trails, which tend to not be groomed, and can offer a variety of terrains. This type of shoe usually has sturdier materials, toe guards and underfoot plates for additional protection, a supportive midsole and upper to deal with hard impacts and unstable surfaces, deeper lugs with more varied patterns, and thicker soles.
Off trail shoes are for the toughest of terrains, many of which are completely ungroomed. In addition to the features of rugged trail shoes, these include extremely tough midsoles and other materials, a high amount of rigidity to prevent your feet from twisting on uneven surfaces, and some type of waterproofing.
With this information about trail shoes in mind, the first step you should take is exploring the trail on which you plan to run. Find out what type of terrain they offer, and then you will have a better sense of what type of trail running shoes will best serve you.