After a long hiatus, but continual training regiment on the road, I returned to trail running. If you enjoy running just for the sake of running, get out on the trail. I thought to provide some basic concepts for those just getting started. Please note these are thoughts from an amateur with plenty of experience running trails that thinks it is worthwhile to give some tips. Perhaps these concepts only work for me.
Asphalt can be fun on its own, but if you live close enough to a trail head, there is a stark difference running in dirt and taking in the surrounding environment. For one, you are not sucking in someone else's tail pipe and the ground is much more pliable in comparison. The views you will take in from running trails are well worth any added elevation you will struggle through. Concentrating on your steps and traversing rocks is a challenge in itself and definitely works your muscles in a different fashion than mundane flat roads.
If it is your first venture out and you plan on running up or down hill, I would recommend bringing some gloves. A key factor when running trails is to lift your legs as high as possible to clear any rocks or other features that can cause an abrupt halt to the fun and leave you eating rocks or worse. I learned the hard way and have made good use of my gloves. After becoming acclimated to the trail by learning the ups and downs, twists and turns, I shed the gloves due to sweaty hands, but some may opt to stick with them as it only takes one errant rock or root to screw your day.
The other key aspect to getting started on trail running is good trail shoes. I like the Brooks brand and went with their Cascadia Shoe. They are designed with one of the ultra trail runner's Scott Jurek, so I figured they couldn't be half bad. They turned out to be like slippers with what they call ballistic protection outer sole or some other marketing B.S., but in the scheme of things, you won't feel rocks under foot. They also breathe well and keep your feet dry on long ventures into the wilderness, even in swamp ass desert AZ in the middle of summer.
After some extensive trail running, I have noted a marked increase in speed when running on flats. Clearly you need to be at a point in your fitness to handle trail running and flat road running will certainly help you get to that point, but once you are there, it can be one of the more exhilarating means of physical fitness. The things you will see and pure adrenaline developed from down hill speedy madness is well worth the experience and threat of dotting your carcass with granite. While, Mountain bikers and skiers have known to perish from taking a downhill spill, I have yet to hear of a runner to pick up enough speed to meet such a fate, but you will still feel a lot of pain from a false step, so pay attention.