I have read the lists, you have read the lists...those magazine articles that declare what you need in order to be able to get started trail running. Some of the things on the list are pretty self-evident, but others...you only need if you live in more mountainous areas and intend on being out there for several hours with perhaps the possibility of running into harsh weather.
Most of us have jobs and families, so going on long runs in extreme conditions is fairly rare. While long runs can be several hours, the typical trail run for a lot of newbies and more experienced trail runners tends to be in the sub-2 hour category. The trails here in Iowa are much different than in the North East where I started trail running, and the mountainous states where I have only been able to do a few runs while on vacation. That said...here's some thoughts on what you really need for a trail run in Iowa.
Shoes: A lot of Iowa trails seem to be near rivers, lakes, and other bodies of water. If it is dry out and hasn't rained recently, you likely can get away with your road shoes. If the trail is hilly, (yes, we have those in Iowa, some actually fairly steep), and/or wet, then trail shoes will definitely help. Right now I am rotating through 5 pairs of shoes, 2 pairs of Brooks Adrenaline road shoes, 2 pairs of Montrail Fairhavens, and 1 pair of Salomon 3D Pro Ultra Sense. Most of the trails I run on around Iowa I could run in the Adrenalines, but if it gets rainy, then the other shoes are much more helpful. The Salomons at times can actually be a bit overkill, just like the Adrenalines are not quite enough if the mud is slick as snot like up at Zumbro this year in MN. P.S. Inside those shoes...use any socks you want, but Injinji toe socks rock!
A Willingness to Try New Food: Bugs are protein. Right now if you go out in the woods, you will likely swallow a gnat, mosquito, or some other type of annoying, flying bug. You can try to hack it out, but if it gets caught in your pipes, it takes a lot of work...and you'll have to decide if attempting to puke it out is worth it or if you should just swallow it and down a water enhanced chaser.
Other food items to bring with you, or leave at your car-aid station: bananas, water, sports drink/gel of choice, salt tabs. Right now I typically use VFuel gels, Nuun sports tablets, Gin-gins, Stretch Island Fruit leathers, bananas, Hammer Nutrition Endurolytes and water. The food items are all small enough to put a variety of them (except for the banana!) in a small waist pack or the pocket on your handheld or in your shorts.
BUT: If your run is an hour or less, you really don't need to take anything with you at all. If its's hot, you could take a smaller hand-held (10oz or less) and maybe a Gin-gin or two. (Ginger is great for nausea and the little bit of sugar in them is a boost too.)
Bug Spray and/or Sun Screen: So...I hate putting either one of these things on my body. Bug spray I try to limit to my ankles and shoes if possible. Sun screen you really only need if the trails are not shaded. Also, if you go earlier in the day or later in the day, avoiding the hottest times, you will less likely need sun screen. Even on very exposed runs in the sun, I only usually wear sun screen if I am running in between 10am - 4pm. A cap or visor can also help to shield your face from some of the exposure.
Lightweight/Light colored clothes: Just as in most of our Summer lifestyle, the lighter colored and lighter weight the clothing is, the more likely it will be comfortable as you trail run.
Hours vs. Miles: As others have noted, focus less on how many miles you get in and more so on time spent on your feet. On average most say that your trail splits will be about 1 minute slower than on the roads. That may be true if the trail is fairly flat, not too technical or twisty. However, there are times when the trails are so technical, so hilly, or so twisty, that you will be many minutes per mile slower. For example, on one long trail run recently, I ran a little over 16 miles in 4 hours, and that was with the last couple of miles on the roads! The trails where I was running were very steep. I also had to do a bit of trail finding that included running one stretch through stinging nettle for several minutes. Then, a week later, I went on a 4 1/2 hour run around our town, doing multiple loops on several different surfaces: pavement, trail, grass, and gravel and ran 24 miles while dealing with a case of vertigo. So, where you run affects how fast you run more than you think. Trails are typically slower than roads.
That's really it. If you already run or exercise in some other form, you likely have most of what you need to start trail running.
Now, go out and have some fun!