In deep forest, it can be difficult to ascertain direction: The sun's position may be obscured, prominent landmarks are sometimes hard to find, and vistas of timber can look repetitive. Make sure you carry a compass and a good map. GPS units are helpful, but can have difficulty communicating with satellites under heavy canopy.
Thermoregulating and Weather
An obvious joy of woodland hiking in deep summer is the cool, shadowy refuge the forest offers on hot days. Keep this in mind if you're planning your own route across country, or taking a long day hike or backpack on trail: You can try to schedule a woodsy passage for the high temperatures and sun of mid-afternoon. Forests can also shield from rain, even snow, and certainly lower woods are safer places to hole up in than bald slopes and summits during lightning storms.
Be especially careful when hiking in wooded areas followed storms and wildfires. Timber felled by wind but propped against others, as well as loose branches hanging in the canopy, are often termed "widow-makers" for their unnerving tendency to topple suddenly. And for several years after a major wildfire, a burned forest may contain a dangerous number of precarious standing snags; be on guard in scorched groves during high wind.
Reading the Woods
You can learn a lot about the life history of a forest through a simple stroll. Consider the spacing and dimension of the trees: Old-growth groves, increasingly rare, are often defined by aloof trunks of massive proportion, shade from the substantial canopy keeping the understory sparse and open; younger forests are usually denser, with much slimmer trees and lots of shrub- and sapling-thickets. Watch for nurse logs---felled, decaying trunks fueling the growth of ferns, shrubs, and even new saplings out of its very cadaver. Hypothesize the genesis of those mysterious openings in deep woods---the grand collapse of an old veteran tree, flooding the forest floor with new sunlight? Severe wildfire or storm? In the mangrove forests and tropical hardwood hammocks of southwestern Florida, for example, hurricanes regularly flatten groves, leaving a few pale, ghostly snags standing.
While birds, squirrels, rabbits, and insects are commonly encountered on woodland jaunts, larger animals are rarely seen---not least because of the denseness of the cover. To increase your chances of spotting wildlife, a good hiking method is to stop every few minutes and listen to the forest around you. Remember to make plenty of noise in bear country, especially when trails enter thick tunnels of vegetation, streamside groves where sound is drowned out by running water, or berry thickets during the fruiting season. In wintertime deciduous forests, keep your eyes to the canopy: This is a great time to spot the unoccupied nests of big birds, like raptors, crows and great blue herons. Note the patterned holes left in standing snags by woodpeckers.
Even those not venturing off-trail in forests should be aware of the small minority of plants that can cause injury to the unwary hiker. Learn to recognize rash-causing species like poison ivy, poison oak, poison sumac or poisonwood---one or more of which are found across most of the United States, often shouldering trails. Other types like devil's club, a striking, impressively-spined plant of the Pacific Coast mountains, or blackberry can form near-impenetrable thickets.