One of my favorite uses of Google Earth is to plan and scope out upcoming backcountry trips. Currently, I am plotting a overnight camping trip on the Pacific Crest Trail (PCT) near Mount Shasta in California. There are a number of ways to do this:
Navigate to the area - Tilt and check out the terrain. This will give you a sense of what you will find on your trip, including natural features, lakes, etc.
Display existing trails - (Layers panel > Gallery > Trimble Outdoors Trips) This layer has some excellent information about trails and the PCT in particular. It includes tracks, trailheads, distances, landmarks, pictures and more.
Import a map as an image overlay - I pulled in a USFS map for trails in the area, which included additional information about distances and landmarks.
Display names for natural features - (Layers Panel > Places of Interest > Geographic Features) These names are extremely helpful because they often correspond to topographical maps. Note that these names do not appear until you zoom in a bit.