If you ever find yourself lost in nature, first of all, take a deep breath and don’t panic. If you have a compass (or a smart phone with a compass app), use it to help find your way out. However, if you ventured out unprepared or cannot get reception on your smart phone, you can actually enlist the help of nature to guide you home!
First, find a nearby tree with a large diameter and observe the thickness and direction of the branches. In the northern hemisphere, the branches on the south-facing side of the tree will be fuller, while branches on the north-facing side will be thinner and grow upwards. Depending on the tree, this is usually easiest to see if you look up along the trunk. Also, the north-facing side of the tree would be more humid than the south-facing side, which is something most species of moss likes, and consequently, there will be more of it on the north face.
If there aren’t any reliable trees nearby (and you're in the northern hemisphere), you could look at how snow melts. In the Spring in the mountains, snow will melt faster on the south face of rocks, or in south-facing slopes. Also, vegetation and undergrowth will typically be thicker on the south-facing slopes.