GPS receivers definitely aren't something you can take out of the box and use with any degree of proficiency. I spent several weeks working with my Magellan Meridian Gold before I actually relied on it.
One feature that most have though is fairly easy to use, and is perfect for finding your truck or hunting camp is the MOB (Man Overboard) feature. Check the instructions for your individual unit, but it basically involves simply pushing the MOB at your truck or camp which memorizes the coordinates. Then just call up the coordinates from the database and hit "goto".
There is one problem with MOB though. The return route will be a straight line only. This could be a problem if you're traversing treacherous terrain, especially at night.
The answer to that is the "backtrack" feature that most have. That allows you to re-trace your exact route within about 30 feet to either side.
I fish a lot at night, and around here, fog can come up on the water in a heartbeat, and it's often so thick that I can't see the bow of my boat. GPS is a lifesaver when that happens.
(Edit) Interesting subject, but this probably is more appropriate for the Gear & Accesories Forum, so, off we go.